Catalysts for hydrotreatment of heavy hydrocarbon oils containing asphaltenes

ABSTRACT

A catalyst for hydrotreating a heavy hydrocarbon oil containing asphaltenes comprises a porous carrier composed of one or more inorganic oxides of at least one element selected from among those of Groups II, III and IV of the Periodic Table, and at least one catalytic metal component composited with the carrier. The metal of the catalytic metal component is selected from among those of Groups VB, VIB, VIII and IB of the Periodic Table. The catalyst contains about 1 to 30% by weight of such catalytic metal component and has the following pore characteristics with regard to its pores having a diameter of 75 Å or more: an average pore diameter APD of about 180 to 500 Å, a total pore volume PV, expressed in cc/g, being equal to or greater than a value X ##EQU1## the volume of pores with a diameter of about 180 to 500 Å being at least about 0.2 cc/g, the volume of pores with a diameter of at least 1,500 Å being not greater than about 0.03 cc/g, and a total surface area being at least about 60 m 2  /g. The catalyst has an average catalyst diameter ACD, expressed in millimeters, of not greater than a value of the formula, ACD=(APD/100) 0 .5. Disclosed also are a method of preparing such a catalyst, and a process for hydrotreating a heavy hydrocarbon oil containing asphaltenes in the presence of such a catalyst.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a novel and improved catalyst which iseffective for the treatment of a heavy hydrocarbon oil containingasphaltenes, especially for the decomposition and conversion ofasphaltenes into lower molecular compounds, and the removal of metalsand sulfur from asphaltenes. This invention is also directed to a methodof preparing such a catalyst and to a process for hydrotreating anasphaltene-containing heavy hydrocarbon oil using such a catalyst.

2. Description of the Prior Art

The heavy hydrocarbon oils to which this invention is applicable includereduced crude oils, vacuum residues, certain crude oils produced inSouth America, etc., heavy oils extracted from tar sand or oil sandproduced in Canada, etc., and mixtures thereof. These hydrocarbon oilsusually contain asphaltenes, heavy metals, sulfur compounds, nitrogencompounds, or the like. The term "asphaltene" used herein means asubstance which is insoluble in normal heptane (n-heptane), and mostlycomposed of high molecular condensed aromatic compounds. These compoundsare associated with one another to form micellar colloids in heavy oils.Specific examples of such heavy hydrocarbon oils include high-asphalteneand high-heavy metal Venezuelan crude oil having a specific gravity(ÅPI) of 9.4, an asphaltene content of 11.8% by weight, a vanadiumcontent of 1,240 ppm, a sulfur content of 5.36% by weight and a nitrogencontent of 5,800 ppm, atmospheric residues from Canadian tar sandextracted oil and having a specific gravity (ÅPI) of 9.2, an asphaltenecontent of 8.1% by weight, a vanadium content of 182 ppm, a sulfurcontent of 4.41% by weight and a nitrogen content of 4,200 ppm, andvacuum residue of Middle and Near East oil and having a specific gravity(ÅPI) of 5.1, an asphaltene content of 14.6% by weight, a vanadiumcontent of 165 ppm, a sulfur content of 5.24% by weight and a nitrogencontent of 4,000 ppm.

Table 1 shows the properties of typical heavy hydrocarbon oils. In thetable, the letters A to F indicate the following oils, respectively:

    ______________________________________                                        A: Boscan crude oil                                                                           B: Athabasca bitumen                                          C: Khafji vacuum residue                                                                      D: Gach Saran vacuum residue                                  E: Kuwait vacuum residue                                                                      F: Gach Saran atmospheric residue                             ______________________________________                                    

                  TABLE 1                                                         ______________________________________                                        Properties of feedstock oils                                                            A    B      C       D    E     F                                    ______________________________________                                        Specific    9.4    9.2    5.1   4.8  6.0   16.4                               gravity, API                                                                  Carbon, wt %                                                                              83.06  83.11  83.11 84.85                                                                              83.42 85.35                              Hydrogen, wt %                                                                            10.49  10.50  10.05 10.36                                                                              10.12 11.50                              Sulfur, wt %                                                                               5.36   4.41  5.24   3.67                                                                              5.25  2.62                               Nitrogen, wt %                                                                             0.58   0.42  0.40   0.65                                                                              0.42  0.36                               Conradson carbon                                                                          15.8   13.5   23.8  21.6 23.0  8.88                               residue, wt %                                                                 Asphaltenes, wt %                                                                         11.8   8.1    14.6  7.8  4.9   2.87                               Metals, wt ppm                                                                Ni            106   79    53     92  35    42                                 V           1,240  182    165   298  117   130                                ______________________________________                                    

As shown above, a heavy hydrocarbon oil contains a very large amount ofimpurities, such as sulfur and nitrogen compounds, vanadium and nickel.Such impurities are contained in the asphaltene fraction in concentratedstate, and make catalytic hydrodesulfurization difficult. Heavyhydrocarbon oils having such a high content of asphaltenes existabundantly in nature, and while they are considered as promisinghydrocarbon resources, they are presently used merely for producingextremely low grade fuel oil or asphalt for pavement of roads. Whenthese heavy hydrocarbon oils are used as fuel and burnt, they produceoxides of sulfur, nitrogen, heavy metal, etc. which cause air pollution.Despite these disadvantages, heavy hydrocarbon oils containingasphaltenes and heavy metals are important under the present politicaland economical situation facing energy crisis due to the depletion ofhigh quality petroleum resources in the near future. It is stronglydesired to develop technology which is effective for converting thoseheavy hydrocarbon oils to more useful hydrocarbon oils containing nosubstance causing environmental pollution, and which are substantiallyfree from any asphaltenes or heavy metals.

Various kinds of catalysts and desulfurization processes have beenproposed for hydrodesulfurization of a heavy hydrocarbon oil having arelatively low asphaltene and heavy metal content to obtain a highergrade desulfurized oil, and some of them have already been usedcommercially. A typical process employs a fixed or ebullated bed bywhich a heavy hydrocarbon oil is hydrodesulfurized directly. Thedevelopment of this direct hydrodesulfurization process is largelyattributable to the improved catalyst performance [M. W. Ranney,Chemical Technology Review No. 54, "Desulfurization of Petroleum", NoyesData Corporation, New Jersey (1975)]. It is, however, well known amongthose of ordinary skill in the art of petroleum refining that a numberof economical disadvantages may result from the use of this process ifthe oil to be treated contains large amounts of asphaltenes and heavymetals, because the macromolecules of asphaltenes are colloidallydispersed in the oil and are not able to diffuse easily into the activesites in the pores of the catalyst. This seriously inhibits thehydrocracking of asphaltenes, and the presence of the asphaltenesinhibits desulfurization and other reactions for hydrotreating thehydrocarbon oil. Another obstacle to the practical application of thedirect hydrodesulfurization process lies in the formation of coke andcarbonaceous materials highly promoted by the presence of asphaltenes,leading to a sharp reduction in the activity of the catalyst. Theformation of such carbonaceous materials does not only occur in theintraparticles of the catalyst, but also in the interparticles among thecatalyst particles. If the feedstock oil contains a large amount ofasphaltenes, an increased amount of carbonaceous material derived fromasphaltenes is deposited into the spaces among the catalyst particles,and the gummy carbonaceous sediment unites the catalyst particlestogether. This causes blocking of the catalyst particles and plugging ofthe catalyst bed, so that there occur serious problems, such asmaldistribution of the reactant flow through the bed, and an increaseddifferential pressure across the bed.

A further serious disadvantage of the direct hydrodesulfurizationprocess resides in an extremely shortened catalyst life which is due tothe poisoning and pore-plugging action of the metals containedabundantly in the feedstock oil, namely due to the metal deposition onthe catalyst active surfaces.

The catalytic hydrotreatment of heavy hydrocarbon oils, using theconventional catalyst, requires an extremely high catalyst consumptionrelative to the amount of the oil being handled, and even if theaforementioned disadvantages may have been overcome, the conventionalcatalysts make it imperative to set severe conditions for the reactions,which accelerate catalyst deactivation, in the event the operation isprimarily intended for decomposing asphaltenes selectively to obtainlight oil. Moreover, a high rate of gasification resulting from thesecondary cracking of light oil prevents production of light oil at ahigh yield, and an increased hydrogen consumption causes a seriousproblem in the economy of the operation. It has also been pointed outthat the gummy matter contained in the product oil lowers its thermalstability, and that sludge material is likely to settle down, causingphase separation (U.S. Pat. No. 3,998,722). Accordingly, in order toobtain a low sulfur fuel oil by hydrodesulfurization of a heavyhydrocarbon oil having high asphaltene and heavy metal contents, e.g.,containing at least about 5% by weight of asphaltenes and at least about80 ppm of vanadium, pretreatment of the heavy hydrocarbon oil hascurrently been required [C. T. Douwes, J. Van Klinken et al., 10th WorldPetroleum Congress, Bucharest, 1979, PD-18(3)]. A variety of processeshave been proposed for the pretreatment, and can be classified into thefollowing two groups. One of the groups covers the processes forremoving asphaltenes and heavy metals from the feedstock oil byextraction, such as solvent deasphalting or otherwise physically, or byheat treating, such as coking. These methods, however, produce aconsiderably large quantity of by-products, such as deasphalting residue(asphalt) or coke, and the effective utilization of these heavyby-products is not feasible, since they contain highly concentratedimpurities, such as heavy metals, sulfur and nitrogen. As the quantityof the by-products increases with an increase in the asphaltene contentof the feedstock oil, the application of these processes is noteffective.

Another group involves hydrotreatment of a heavy hydrocarbon oil in thepresence of an appropriate catalyst, mainly for the hydrodemetallizationthereof to thereby reduce the poisoning to the catalyst by heavy metalsin the subsequent catalytic hydroprocessing. There have been proposedvarious types of catalysts and processes for such pretreatments. Forexample, there are known demetallization processes using inexpensivecatalysts, such as natural minerals containing alumina, such as bauxite,ores such as manganese nodules and nickel ore, and industrial waste suchas red mud and spent desulfurization catalysts (U.S. Pat. Nos.2,687,985, 1,769,758, 2,771,401, 3,839,187, 3,876,523, 3,891,541 and3,931,052 and Japanese Laid-Open Patent Applications Nos. 13236/1972,21688/1973, 5402/1974, 121805/1974, 122501/1974, 78203/1978 and3481/1979). These catalysts are, however, unsatisfactory. Some of themhave certainly high activity for demetallization, but still encounterthe problem of deactivation by metal deposition because they have asmall pore diameter or an insufficient pore volume. Other catalysts havean insufficient surface area resulting in an insufficient activity fordemetallization, thereby requiring the treatment to be carried out in arelatively high temperature operation. Consequently, carbonaceous matteris formed by polycondensation, etc. of high molecular compounds such asasphaltenes, and the catalysts are strongly deactivated by coke. Thus,these pretreatment methods are faced with a number of problems, such asreduction in the activity of the demetallization catalyst duringcontinuous operation, and necessity of the regeneration or disposal ofthe spent catalyst. Although demetallization with such catalysts may tosome extent reduce the poisoning of the catalyst by heavy metals in thesubsequent desulfurization processing, it hardly serves to removemacromolecules of asphaltenes from a heavy oil, and leaves outstandingproblems of catalyst poisoning, plugging, or the like by asphaltenes.

There have been many proposals made for improving the demetallizationactivity by specifying the kind and quantity of the catalytic metalcomponent for hydrotreatment to be used in the catalyst which is similarto those for the hydrodesulfurization of heavy hydrocarbon oils (see,e.g., U.S. Pat. Nos. 2,577,823, 2,730,487, 2,764,525, 2,843,552,3,114,701, 3,162,596, 3,168,461, 3,180,820, 3,265,615, 3,297,588,3,649,526, 3,668,116, 3,712,861, 3,814,683, 3,876,680, 3,931,052,3,956,105 and 3,960,712, and Japanese Patent Publications Nos.20914/1971, 33223/1971 and 9664/1974). There are, however, problems inthe practical application of these catalysts for thehydrodemetallization of heavy hydrocarbon oils having high asphalteneand heavy metal contents, since various difficulties, such as thepoisoning of the catalyst by asphaltenes and heavy metals, still remainsubstantially unsolved as pointed out with reference to thepreviously-described hydrotreating catalyst. Various hydrotreatingprocesses have been proposed for the purpose of overcoming theseproblems (U.S. Pat. Nos. 1,051,341, 2,890,162, 3,180,820, 3,245,919,3,340,180, 3,383,301, 3,393,148, 3,630,888, 3,640,817, 3,684,688,3,730,879, 3,764,565, 3,876,523, 3,898,155, 3,931,052, 3,902,991,3,957,622, 3,977,961, 3,980,552, 3,985,684, 3,989,645, 3,993,598,3,993,599, 3,928,176, 3,993,601, 4,016,067, 4,054,508, 4,069,139 and4,102,822, Japanese Patent Publications Nos. 38146/1970, 18535/1972,17443/1973, 16522/1974, 18763/1974, 18764/1974, 3081/1975, 26563/1979,and Japanese Laid-Open Patent Applications Nos. 2933/1971, 5685/1972,44004/1974, 121805/1974, 123588/1975, 31947/1973, 9664/1974,144702/1975, 160188/1975, 4093/1976, 55791/1976, 30282/1977, 50637/1977,22181/1978, 23303/1978, 145410/1977, 36485/1978, 2991/1979, 11908/1979,14393/1979, 23096/1979, 104493/1979, 112902/1979 and 125192/1979).

The aforementioned processes proposed for attaining this purpose can beclassified roughly into the following groups with respect to thecatalyst to be used:

(1) Process for hydrotreating characterized by using a catalyst havingsmall pores (i.e., catalyst having a peak of a pore diameter at about100 Å or below in its a pore volume distribution);

(2) Process for hydrodesulfurization and demetallization characterizedby using a catalyst having middle pores (i.e., catalyst having a porevolume which is for the greater part occupied by pores having a diameterin the range of about 100 Å to 200 Å);

(3) Process for hydrodemetallization characterized by using a catalysthaving macro pores (i.e., catalyst having a pore volume of which thegreater part is occupied by pores having a diameter of about 200 Å orabove);

(4) Process for hydrodemetallization and desulfurization characterizedby using a catalyst having both the pore characteristics mentioned at(2) and (3) above;

(5) Process for hydrodesulfurization and demetallization characterizedby using a catalyst having a double-peak in its pore volume distributiondefined by both the pore characteristics mentioned at (1) and (3) above;

(6) Process for multistage hydrotreatment with a combination of sometreatments using the aforementioned catalysts;

(7) Process for hydrotreating using a catalyst comprising a acomposition which is substantially the same as one of the aforementionedcatalysts, but having a specific shape; and

(8) Process for hydrotreating characterized by the mode and conditionsof the reaction.

None of the processes listed above is, however, satisfactory, since noneof them gives a basic solution to the aforementioned technical problemsfound in the hydrotreatment of heavy hydrocarbon oils containing largeamounts of asphaltenes and heavy metals. The problems involved in eachof these proposed processes will hereunder be pointed out, together withits characteristic features.

The process belonging to the group (1) is intended for coping with thedifficulties which are due to the metal compounds present in heavyhydrocarbon oils, and uses a catalyst having a narrow pore volumedistribution defined by small pores which are capable of excludingmacromolecules of asphaltenes. According to this method, therefore,asphaltenes are hardly demetallized or desulfurized, but metal and cokeare likely to deposit near inlets of pores. Because of thesedisadvantages, this process is unsuitable for the treatment of a heavyhydrocarbon oil containing large amounts of asphaltenes and heavymetals, and is applicable only to oil having a heavy metal content ofabout 50 ppm or below.

The process of the group (2) is widely utilized on a commercial scalefor the hydrodesulfurization of an atmospheric residue, and makes itpossible to lessen to some extent the reduction in the activity of thecatalyst which is due to the heavy metal and asphaltenes in thefeedstock oil. However, the effect of this method depends mainly on themetal content of the feedstock oil, and the application of the processis substantially limited to oil having a metal content of about 80 to100 ppm, or below. The diameters of the pores in the catalyst used forthis process are sharply reduced at the mouths thereof by deposition ofmetals therein, and the diffusion of macromolecules of asphaltenes orthe like into the pores is greatly inhibited. Therefore, there arenecessarily limitations to the asphaltene content of the feedstock oilwhich can be treated by this method, and the application of this methodis limited to a feedstock oil having an asphaltene content of about 5%by weight or below.

The process of the group (3) uses a catalyst of which nearly all thepores have a diameter of at least about 200 Å in order to facilitatediffusion of metal compounds into the pores. The increased pore diameterfacilitates the diffusion into the pores of high molecular compoundshaving a high heavy metal content, but as the catalyst has a sharplyreduced pore surface area, its activity for demetallization is notsubstantially improved. If the volume of macropores is increased toenlarge the pore surface area, coke precursors, such as asphaltenes,stay in the pores for a long time, thereby promoting the cokingreaction, with a resultant increase in the deposition of coke in thecatalyst pores. Thus, most of the catalysts employed for carrying outthis method have a relatively low activity for demetallization. If forhydrotreating, the conditions for the reaction are made severer in orderto raise the demetallization activity of the catalyst to a practicallyacceptable level, and particularly if the reaction temperature isincreased, there occur an excess consumption of hydrogen, and otherproblems which are similar to those already pointed out with respect tothe process in which inexpensive material, such as bauxite, is used as acatalyst. In the event a macropore catalyst with many pores having adiameter of at least about 400 Å is used, a slight increase in thesurface area does not improve the performance of the catalyst very much,since the amount of the coke to be deposited also increases. Furtherdrawbacks which are common to such a molded catalyst include aninsufficient mechanical strength which is likely to cause disintegrationof the catalyst due to its breakage and abrasion when it is charged intothe reactor, and during the operation. According to this process, thecatalyst is primarily intended for demetallization, and does not haveany appreciable effect on the decomposition of asphaltenes.

The process of the group (4) is an improvement over the processes (2)and (3), and uses a catalyst having specifically controlled ranges ofpore volume and particle diameter in a pore diameter range of at least100 Å. This process is, however, primarily intended for demetallizationof the feedstock oil as a whole, or simultaneous demetallization anddesulfurization, and is not considered complete for eitherdemetallization or desulfurization. The process is not considered toprovide a very satisfactory improvement from the standpoint of efficientuse of the catalyst, either.

Generally, a heavy hydrocarbon oil contains large amounts of impurities,such as heavy metals and sulfur compounds, which are widely distributed,not only in high molecular fractions such as asphaltene fractions, butusually considerably in relatively low molecular hydrocarbon oilfractions as well. It is practically difficult to obtain a catalysthaving pores with a diameter range which is suitable for thedemetallization and desulfurization of both asphaltene and low molecularfractions, and a pore surface area which is sufficiently large tosatisfy both of the purposes. It is actually impossible to obtain asingle catalyst which is capable of performing the functions ofdemetallization and desulfurization simultaneously to an optimum degree.The molecular sizes of the heavy metal and sulfur compounds which aheavy hydrocarbon oil contains differ over a wide range, and theirdiffusion into the catalyst pores has largely different effects on thereactions of each molecule. The rates of desulfurization anddemetallization of asphaltenes are extremely low as compared with thoseof other light oil fractions. Moreover, a comparison between thedemetallization and desulfurization rates reveals that demetallizationis more likely to be affected by the intrapore diffusion. It ispractically impossible to accomplish with a single catalyst thehydrodemetallization or desulfurization of a heavy hydrocarbon oilcontaining large amounts of asphaltenes and heavy metals at asubstantially satisfactory reaction rate, since it means an excessiveneed for the total surface area and total pore volume of the catalyst.The surface area of a catalyst is determined almost solely by the porediameter and pore volume, and an increase in the pore diameter resultsin a sharp reduction of the surface area, as already pointed out.

Thus, the maximum pore volume of the catalyst for the group (4) isinevitably limited to the level which the mechanical strength requiredthereof permits, and the catalyst fails to show any such degree ofactivity as the optimum catalysts for the groups (2) and (3) can provideindividually for desulfurization or demetallization. Those portions ofthe catalyst which are provided with pores having a diameter of about100 to 200 Å lose their catalytic activity rapidly due to pore pluggingby metal accumulation, while the remaining portions with larger poreshas only a limited surface area and do not contribute to the reaction.The catalyst for the group (4) does not provide any appreciably improvedefficiency, since it does not always permit a sufficiently large amountof metal to be accumulated thereon before the rates of the variousreactions involved can be kept equal, as opposed to the optimumcatalysts for the groups (2) and (3). In order to overcome thesedisadvantages, it is necessary to use a catalyst composed of very fineparticles, but such a catalyst is not suitable for a fixed or ebullatedbed system which is usually employed for the hydrotreatment of a heavyhydrocarbon oil. As the demetallization of heavy hydrocarbon oils isgenerally determined by the rate of intrapore diffusion, the overallreaction velocity shows a decrease as an exponential function of thediameter of the catalyst particles.

The process of the group (5) is based on the fact that in thehydrotreatment of heavy hydrocarbon oils, desulfurization is not verylargely influenced by intrapore diffusion, while demetallization islargely affected by it. According to this process, there is used acatalyst provided with both small pores having a diameter not greaterthan about 100 Å, and macropores having a diameter of at least about 500Å, or even at least about 1,000 Å. Although this catalyst does certainlyrelax the limitations relating to the diffusion of metal-containing highmolecular compounds into the pores, it shows a sharp reduction inactivity due to metal accumulation in the pores having a diameter notgreater than about 100 Å, and the mouths of these pores are likely to beblocked, as is the case with the catalyst used for the group (1). Thus,the catalyst for the group (5) fails to maintain a high activity for along time for the feedstock oil having a high metal content, andeventually, only the larger pores act mainly for demetallization.Therefore, it is not considered to have an improved efficiency over thecatalysts for the groups (1) and (3) which are used individually.

Groups (6), (7) and (8) have been proposed to improve the efficiency ofhydrotreating of heavy hydrocarbon oils by selecting a catalystcomposition from the groups (1) to (5), but fail to provide any basicsolution to the problems inherent in the catalysts for the groups (1) to(5).

It will be noted from the foregoing that the various proposals made forthe hydrotreatment of heavy hydrocarbon oils share a number ofdisadvantages. First of all, there has been no proposal suggesting anoptimum catalyst for the decomposition of asphaltenes. Moreover, none ofthe processes proposed for simultaneous desulfurization anddemetallization with a single type of catalyst is well aware of the factthat the great difference in molecular size between asphaltene and theother oil fractions leads to a large difference in the reaction velocitybetween desulfurization and demetallization.

As already pointed out repeatedly, the pretreatment of oil for effectivereduction and removal of asphaltenes therefrom is essential forobtaining a high grade hydrocarbon oil by hydrotreating the feedstockoil containing a large amount of asphaltenes. There has been proposed nocatalyst that is suitable for that purpose. A number of attempts have,however, been made recently for decomposing asphaltenes in heavyhydrocarbon oils. For Example, various processes have been proposed inJapanese Patent Publications Nos. 33563/1976, 42804/1977 and 5212/1978which have recently been issued. These processes propose conversion of aheavy hydrocarbon oil to a light hydrocarbon oil by dispersing vanadiumsulfide, e.g., vanadium tetrasulfide, in the heavy hydrocarbon oil toform a slurry mixture, or mixing oil-soluble vanadium, e.g., vanadiumresinate, into the heavy oil, and activating the vanadium at hightemperature and hydrogen pressure, so that fine particles of theactivated vanadium sulfide may be circulated for use as the catalyst. Inorder to obtain a satisfactory rate of decomposition for asphaltenes,however, it is necessary to raise the reaction temperature, or increasethe concentration of the catalyst. Moreover, it can easily be supposedthat these processes may reveal new and serious disadvantages when putinto practice, since they all involve a slurry process in which avanadium sulfide catalyst having no carrier is used. A typical slurryprocess for catalytic hydrotreatment at high temperature and pressurehas long been known as a process for direct liquefaction of coal. It isknown that these slurry processes share a number of drawbacks which mustbe eliminated before they can be adopted on an industrial basis. Forexample, the operation is complicated, troubles, such as blocking of thepassage, are likely to occur, and special technical consideration mustbe given to the recovery of the fine-grained catalyst from the apparatusused and the heavy fractions.

As pointed out, it is difficult to achieve catalytic hydrotreatment of aheavy hydrocarbon oil containing large quantities of asphaltenes andheavy metals, such as vanadium, by any conventional process in a fixedbed or other reaction apparatus which is often used in industry. It isdesired to develop a catalyst conforming to the requirement, and whichcan maintain a high activity for a long period of time.

The members of the group to which the present inventors belong becameaware of the possibility that the establishment of an effective processfor decomposing asphaltenes might be a key to the development of aprocess which would make it possible to obtain a high grade hydrocarbonoil by hydrotreating a heavy hydrocarbon oil containing large amounts ofasphaltenes and heavy metals. They have continued extensive research forseveral years in order to develop a catalyst which eliminates theaforementioned drawbacks of the catalysts known in the art, and which iseffective for the catalytic hydrotreatment of such heavy hydrocarbonoils. As a result, they have found that a catalyst composed of anaturally available clay mineral having a double-chain structure, suchas sepiolite, shows a relatively high activity for the hydrotreatment ofa heavy hydrocarbon oil, particularly for the decomposition anddemetallization of asphaltenes, and have already proposed such acatalyst in U.S. Pat. Nos. 4,152,250 and 4,166,026, Japanese Laid-OpenPatent Applications Nos. 95598/1977 and 1306/1979, etc. Further, theyhave paid their attention to the characteristics of heavy hydrocarbonoils containing a large amount of asphaltenes, particularly asphaltenesper se, and conducted various kinds of analyses and detailed studies forvarious types of oil in order to ascertain the form in which asphaltenesexist in the oils. They have consequently found that different types ofasphaltenes present in different types of oil share a number ofcharacteristics, though the asphaltene contents differ from one kind ofheavy hydrocarbon oil to another. Table 2 shows the results of detailedanalysis for the asphaltene fractions (a) and deasphalted fractions (b)which were obtained by removing asphaltenes from typical types of heavyhydrocarbon oils. In Table 2, the figures in parentheses indicate theweight percentages of the respective substances relative to theircontents in the feedstock oil, and the letters A to E refer to thevarious types of feedstock oil shown in Table 1. The average molecularweight shown in Table 2 was determined by the vapor pressure osmosismethod using pyridine as a solvent.

As is obvious from the results shown in Table 2, all types ofasphaltenes have a lower hydrogen/carbon atom ratio than thecorresponding deasphalted oils, and comprise macromolecules containinglarge quantities of undesirable impurities, such as sulfur, nitrogen,vanadium and nickel. The heavy metals, such as vanadium and nickel, inheavy hydrocarbon oils occupy higher proportions in asphaltenes thansulfur or nitrogen does. Asphaltenes have an average molecular weight ofabout 4,000 to 6,000 which indicates that they comprise macromolecules,but they do not differ very largely from one type of heavy hydrocarbonoil to another. The deasphalted oils have a higher hydrogen/carbon atomratio than asphaltenes, extremely lower vanadium and nickel contents,and mostly an average molecular weight which is less than 1,000. It is,however, noted that at least about 60 to 80% of the sulfur and nitrogencontained in heavy hydrocarbon oils, and generally about 40 to 50% and,in some cases, over 80% of the vanadium and nickel are present in thedeasphalted oils.

                                      TABLE 2                                     __________________________________________________________________________    Properties of (a) asphaltenes in feedstock oil and (b) deasphalted oil                A        B        C        D        E                                         a    b   a    b   a    b   a    b   a    b                            __________________________________________________________________________    Yield wt %                                                                            11.8 87.2                                                                              8.1  89.9                                                                              14.6 83.4                                                                              7.8  91.0                                                                              4.9  92.2                         H/C     1.15 1.59                                                                              1.18 1.52                                                                              1.10 1.48                                                                              1.08 1.48                                                                              1.11 1.48                         atom ratio                                                                    Sulfur wt %                                                                           6.76 5.10                                                                              8.40 4.01                                                                              7.54 4.75                                                                              5.70 3.46                                                                              7.26 4.80                                 (14.9)                                                                             (83.0)                                                                            (15.4)                                                                             (81.7)                                                                            (21.0)                                                                             (75.6)                                                                            (12.1)                                                                             (85.8)                                                                            (6.76)                                                                             (84.3)                       Nitrogen wt %                                                                         1.60 0.40                                                                              1.53 0.36                                                                              0.81 0.31                                                                              1.18 0.59                                                                              0.87 0.41                                 (32.6)                                                                             (60.1)                                                                            (29.5)                                                                             (77.1)                                                                            (29.6)                                                                             (64.6)                                                                            (14.2)                                                                             (82.6)                                                                            (10.2)                                                                             (90.0)                       Metals wt ppm                                                                 Ni      466  58  349  43  193  28  392  66  182  32                                   (51.9)                                                                             (47.7)                                                                            (35.8)                                                                             (48.9)                                                                            (53.2)                                                                             (44.1)                                                                            (33.2)                                                                             (65.3)                                                                            (25.5)                                                                             (84.3)                       V       5390 594 779  109 608  90  1378 205 562  107                                  (51.3)                                                                             (41.8)                                                                            (34.7)                                                                             (53.8)                                                                            (53.8)                                                                             (45.5)                                                                            (36.1)                                                                             (62.6)                                                                            (23.5)                                                                             (84.3)                       Average 5625 690 5460 694 5280 851 4730 940 4302 850                          mol wt                                                                        __________________________________________________________________________

The molecular weight distributions of the asphaltenes and deasphaltedoils were determined by gel permeation chromatography using polystyrenegel as a molecular weight calibrating standard. The results are shown inFIG. 1. In FIG. 1, the results obtained with respect to asphaltene areshown at (a), and those relating to deasphalted oil at (b). Both inFIGS. 1(a) and (b), the axis of abscissa represents the molecularweights of those substances calibrated with polystyrene, and the axis ofordinate indicates the differential refractive indices showing theweight proportions of those substances in relation to their molecularweights. As is obvious from FIG. 1, asphaltenes and deasphalted oilshave widely different molecular weight distributions from each other;asphaltenes are formed from high molecular compounds having differentmolecular weights ranging from about 1,000 to about 50,000, whiledeasphalted oil comprises compounds of which nearly all have a molecularweight in the vicinity of 1,000. Moreover, it should be noted that themolecular weight distribution of asphaltenes does not largely depend onthe type of the heavy hydrocarbon oil.

In short, it is noted that a heavy hydrocarbon oil is composed ofasphaltenes forming macromolecules containing large quantities ofundesirable sulfur, vanadium and nickel, and an oil fraction containingcompounds mostly having a molecular weight not greater than 1,000, andconsidered to be highly reactive for desulfurization anddemetallization, and that the average molecular weight of asphaltenesand its distribution hardly change from one type of oil to another,though its amount may differ with oils. Thus, it is recognized from theresults of the analyses that in order to produce a high gradehydrocarbon oil by catalytic hydrotreatment of a heavy hydrocarbon oil,it is more effective to preliminarily hydrotreat the feedstock oil witha catalyst having a porous structure best suited for the asphaltenemolecules, and a high degree of selectivity and activity for thedecomposition and conversion of asphaltenes into lower molecularcompounds, and the demetallization or desulfurization of asphaltenemolecules, and then hydrotreat the pretreated oil with another catalysthaving a high activity for the desulfurization and demetallization ofthe oil fraction, than to hydrotreat the oil with a single catalyst.

SUMMARY OF THE INVENTION

The present invention provides a catalyst for the hydrotreatment of aheavy hydrocarbon oil containing asphaltenes, which comprises one ormore catalytic metal components composited with a porous carrier. Themetal of the catalytic metal components is selected from the groupconsisting of the metals of Groups VB, VIB, VIII and IB of the PeriodicTable, and the porous carrier is composed of one or more inorganicoxides of at least one element selected from the group consisting of theelements of Groups II, III and IV of the periodic table. The catalyticmetal components occupy about 0.1 to 30% in terms of oxide based on thetotal weight of the catalyst. The catalyst has the following porecharacteristics (a)-(c) with regard to its pores having a diameter of 75Å or more:

(a) An average pore diameter, APD, is between about 180 Å and about 500Å;

(b) A total pore volume, PV, expressed in cc/g, is at least a value Xcalculated according to the following equation: ##EQU2## while thevolume of pores having a diameter of between about 180 Å and about 500 Åis at least about 0.2 cc/g, and the volume of pores having a diameter ofat least 1,500 Å is not greater than about 0.03 cc/g; and

(c) A total surface area, SA, is at least about 60 m² /g. Moreover, thecatalyst has an average catalyst diameter, ACD, expressed inmillimeters, of not greater than a value Y calculated according to thefollowing equation:

    Y=(APD/100).sup.0.5.

The inventors of this invention have conducted further experiments forthe hydrotreatment of various types of heavy hydrocarbon oils by usingmany kinds of catalysts composed of different types of porous inorganicoxides in order to find out a suitable catalyst for the decompositionand conversion of asphaltenes into lower molecular compounds, and thedemetallization and desulfurization of asphaltenes to perform theeffective pretreatment of heavy hydrocarbon oils containing a largeamount of asphaltenes. Based on the results of these experiments, theyhave made an extensive study of the suitability of various catalysts forthe treatment of asphaltenes, particularly their pore structures, toobtain an improved catalyst which is suitable for the purpose intended.As the result, they have discovered that an optimum catalyst for theaforementioned purpose is required to satisfy a specific range ofrequirements for the average pore diameter, pore volume, poredistribution, total surface area and average catalyst diameter of theparticles. The optimum catalyst means a molded catalyst having such adegree of activity as to permit production of a refined oil having asatisfactorily low asphaltene content under industrially permissibleconditions for hydrotreating, including temperature, pressure and liquidspace velocity, and which can maintain such a degree of activity with aminimum loss thereof for a substantially long period of time. Thecatalyst is also required to have a sufficiently high mechanicalstrength which prevents any appreciable breakage or crush of thecatalyst that is recognizable during its use.

The present invention also provides a novel and improved method ofpreparing such a catalyst.

In further aspect of this invention, there is provided a process forcatalytic hydrotreatment, using the aforementioned catalyst, in thepresence of hydrogen in a reaction zone under appropriate operatingconditions, mainly for the purpose of reducing considerable amounts ofasphaltenes and metals from asphaltene-containing heavy hydrocarbonoils.

In accordance with a further aspect of this invention, there is provideda novel and improved process for two-stage hydrotreatment ofasphaltene-containing heavy hydrocarbon oils in the presence of theaforementioned catalyst, whereby high grade hydrocarbon oils may beobtained by reducing the contents of asphaltenes, heavy metals, sulfur,nitrogen, etc. and Conradson carbon residue thereof.

It is, therefore, an object of the present invention to provide a novelcatalyst which is effective for hydrotreating an asphaltene-containingheavy hydrocarbon oil, especially in decomposing asphaltenes andconcomitantly removing heavy metals therefrom.

Another object of this invention is to provide a catalyst which isdevoid of the afore-mentioned drawbacks of the conventional catalystsand which can exhibit a high degree of activity for a long period oftime.

A further object of this invention is to provide a simple andeconomically acceptable method by which a porous catalyst havingspecific surface area, average pore diameter and pore size distributionsuitable for hydrotreating asphaltene-containing heavy oils can beobtained.

It is yet a further object of this invention to provide a process forhydrotreating heavy hydrocarbon oil, especially an oil containing largeamounts of asphaltenes and heavy metals, by which such an oil can beeffectively converted into a substantially asphaltene-free and heavymetal-free light oil.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the detailed description of the invention to followwhen considered in light of the accompanying drawings in which:

FIG. 1(a) is a graph showing the molecular weight distribution of theasphaltene fraction in the feedstock oil;

FIG. 1(b) is a graph showing the molecular weight distribution ofdeasphalted oil;

FIG. 2 is a graph showing the relation between the decomposition rate ofasphaltenes and the amount of metal deposition on the catalyst;

FIG. 3 is a graph showing the rate of sulfur and metal removal fromasphaltenes in relation to the quantity of metal deposition on thecatalyst;

FIG. 4 is a graph showing the relation between the hydrogen consumptionand the decomposition rate of asphaltenes;

FIG. 5 is a graph showing the reaction rate constant for asphaltenedecomposition (ka) in relation to the average pore diameter (APD);

FIG. 6 is another graph showing the relation between the decompositionrate of asphaltenes and the amount of metal deposition on the catalyst;

FIG. 7 is still another graph showing the relation between thedecomposition rate of asphaltenes and the quantity of metal depositionon the catalyst;

FIG. 8 is a graph showing the reaction rate constant for asphaltenedecomposition (ka) in relation to ACD/(APD/100)⁰.5 ;

FIG. 9 is a graph comparing the theoretical and actual values for thecompressive strength of the catalyst;

FIG. 10 is a graph showing the relation between the decomposition rateof asphaltenes and the amount of MoO₃ supported;

FIG. 11(a) is a graph showing the molecular weight distribution for theoils to be hydrotreated;

FIG. 11(b) is a graph showing the molecular weight distribution for theoils which have been hydrotreated;

FIG. 12 is a graph showing the relation between the reaction temperatureand the process time; and

FIG. 13 is a graph showing the relation between the decomposition rateof asphaltenes and the amount of vanadium deposition on the carrier.

DETAILED DESCRIPTION OF THE INVENTION

For the purpose of this specification, the value of the average porediameter, APD, is defined by the following formula, and expressed in Å:##EQU3## wherein PV and SA represent the total pore volume and totalsurface area, respectively, of the pores having a diameter of 75 Å ormore, per unit catalyst weight, which are expressed in cc/g and m² /g,respectively. The total pore volume and the total surface area of thepores having a diameter of at least 75 Å, per gram of the catalyst willhereinafter referred to simply as the pore volume and the surface area,respectively, of the catalyst, unless otherwise noted.

The pore diameter, pore volume and surface area of the catalyst weredetermined by the mercury penetration method [of which details aredescribed in, for example, E. W. Washburn, Proc. Natl. Acad. Sci., 7,page 115 (1921), H. L. Ritter and L. E. Drake, Ind. Eng. Chem. Anal.,17, pages 782 and 787 (1945), L. C. Drake, Ind. Eng. Chem., 41, page 780(1949), and H. P. Grace, J. Amer. Inst. Chem. Engrs., 2, page 307(1956)] using a mercury penetration porosimeter, Model 70 (made by CarloElba of Milano, Italy). The determination was made with a mercurysurface tension of 474 dyne/cm at 25° C., a contact angle of 140° and anabsolute mercury pressure which was varied between 1 and 2,000 kg/cm².The diameter of the pores having a diameter of at least 75 Å can beexpressed by the following formula: ##EQU4##

The average catalyst diameter, ACD, of the catalyst particles accordingto this invention is defined by the following formula, and expressed inmillimeter: ##EQU5##

In this formula, the average volume and average outer surface area ofthe catalyst particles represent the volume and outer surface area,respectively, of a spherical equivalent having a diameter which is equalto the average particle diameter of the catalyst which may be determinedby an appropriate method, for example, by direct measurement, screeningor sedimentation, as specifically set forth in "Particle SizeDetermination", Powder Engineering Society, Nikkan Kogyo Shinbunsha(1975).

The novel catalyst according to this invention is composed of one ormore specific catalytic metal components composited with a porouscarrier formed from inorganic oxides of specific elements, and featuredmost saliently by its physical properties defined within theaforementioned specific ranges. According to the catalyst of thisinvention, its ultimate physical properties, particularly its averagepore diameter, pore volume, pore distribution, surface area and otherfeatures of its pore structure, and the average catalyst diameter of itsparticles have a significant bearing on the effective hydrotreatment ofa heavy hydrocarbon oil containing asphaltenes. According to thisinvention, there has been developed, by restricting those properties tothe specific ranges, an optimum catalyst having a high activity forasphaltene decomposition and an appropriate selectivity for removal ofsulfur and metals from asphaltenes, which have not been achieved by anyknown catalyst. Moreover, the catalyst can maintain its activity for asubstantially long period of time with a high degree of stability, andas it is a molded catalyst, it has a sufficiently high mechanicalstrength.

The features and advantages of the catalyst according to this inventionwill now be described more specifically.

The various reactions which are involved in the catalytic hydrotreatmentof a heavy hydrocarbon oil generally depend more or less on theintrapore diffusion of the reactants into the catalyst. When referenceis made particularly to the decomposition of asphaltenes, the catalystis required to have a different pore diameter from those of thecatalysts which have heretofore been used for removal of sulfur andmetal from a heavy hydrocarbon oil. A larger pore diameter enableseasier diffusion of macromolecules, such as asphaltenes into the activesites of the pores in the catalyst. With an increase in the porediameter, however, the active surface area of the pores is reduced witha resultant lowering of the overall reaction rate. The catalyst shows asatisfactory activity for asphaltene decomposition if it has an averagepore diameter ranging from about 180 Å to about 500 Å, more preferablyfrom about 200 Å to about 400 Å. Pores having an average diameter lessthan about 180 Å show a high activity for removal of sulfur and metalsfrom oil fractions other than asphaltenes, but are not effective forasphaltene decomposition or other reactions involving asphaltenes whichdepends largely on the rate of intrapore diffusion of the asphaltenes.If the feedstock oil contains large amounts of asphaltenes and heavymetals, small and middle pores are easily reduced in size by depositionof metals and coke therein, resulting in diffusion of asphaltenes intothe pores being further restricted, and ultimately, their mouths areplugged by such metal and coke. Therefore, a catalyst having such smallor middle pores is far from being practically acceptable, since thereare easily formed useless pores having substantially no catalyticactivty for the feedstock oil containing large quantities of asphaltenesand heavy metals, though there remain active surfaces inside the poresafter a short period of use.

Thus, pores having an average diameter less than about 1/2Å are noteffective for the decomposition of asphaltenes in a heavy hydrocarbonoil containing large amounts of asphaltenes and heavy metals. Thatportion of the total pore volume of the catalyst which is defined bypores having a diameter less than about 180 Å should be minimized.Specifically, the pore volume defined by pores having a diameter lessthan about 100 Å is preferably less than about 0.1 cc/g, more preferablyless than 0.08 cc/g. Pores having a diameter greater than about 500 Åare large enough for the diffusion of asphaltenes, but such an increasein pore diameter brings about a sharp decrease in the pore surface areaand a reduction in the activity for asphaltene decomposition per unitvolume of the catalyst employed. The larger pores prolong residencetime, and hence, deposition of more coke on the pore surfaces with aresultant reduction in the pore surface activity due to poisoning bycoke. Accordingly, the catalyst can be used with a higher degree ofefficiency with a greater pore volume defined by pores having a diameterin the most effective range of about 180 Å to about 500 Å for asphaltenedecomposition. According to this invention, the total volume of thepores having a diameter of about 180 Å to about 500 Å is preferablygreater than about 0.2 cc/g, more preferably greater than about 0.3cc/g, and most preferably, greater than about 0.35 cc/g. In other words,a catalyst having a high activity for asphaltene decomposition isprovided with a large number of pores having a diameter of about 180 Åto about 500 Å, as compared with smaller or larger pores.

An optimum catalyst for the decomposition of asphaltene in a heavyhydrocarbon oil is required to maintain a sufficiently high level ofactivity and stability for that purpose. For the purpose of thisinvention, a catalyst is considered to have a high degree of stability,if it can for a sufficiently long time remain sufficiently active forforming an oil product having a sufficiently low asphaltene contentwithout causing any such trouble as agglomeration of catalyst particlesand increased pressure drop in the catalyst bed, though its activity maybe reduced by deposition of metal in the pores. The most importantfactor that determines the stability of the catalyst is its pore volume.During the demetallization of a heavy hydrocarbon oil, an increasingamount of metals is deposited in the pores of the catalyst with anincrease in the treatment time, and reduces the volume and diameter ofthe pores, especially their mouth diameter. If the reduction in the porediameter exceeds a certain degree, the diffusion of asphaltenes into thepores is extremely inhibited, and the rate of conversion is sharplyreduced. In order for a catalyst to maintain a satisfactory level ofstability, therefore, it is necessary to ensure that the diffusion ofasphaltenes into the pores not be inhibited, for a sufficiently longperiod of time, by the metals deposited therein, and in this connection,it is necessary for the catalyst to maintain a sufficiently large porevolume to maintain an appropriate average pore diameter of at leastabout 180 Å for asphaltene decomposition for a sufficiently long periodof time. For the purpose of this specification, the term "sufficientlylong period of time" refers specifically to a treatment time of at leastabout 4,000 hours, preferably at least about 6,000 hours, for thetreatment of a heavy hydrocarbon oil with a given reactor filled with orholding a catalyst under the treatment conditions specified according tothis invention. In order to maintain decomposition of asphaltenes forsuch a long period of time, it is necessary that the amount of metaldeposition which is permissible on the catalyst be at least about 50% byweight, and preferably at least about 60% by weight, in terms ofvanadium, relative to the weight of the fresh (or new) catalyst.

The inventors of this invention have discovered that a catalyst whichcan maintain a satisfactory level of stability for a sufficiently longperiod of time is required to have a pore volume, PV, expressed in cc/g,which is equal to, or greater than the value X calculated according tothe following equation: ##EQU6##

The catalyst should have a surface area, SA, of at least about 60 m² /g,preferably at least about 70 m² /g, in order to provide a desirablecatalytic activity.

It is known that the size of the catalyst particles is generally a veryimportant factor in the reactions in which intrapore diffusion prevails[for details, see P. H. Emmett, "Catalysis", Vol. II, ReinholdPublishing Corporation, New York (1955), and C. N. Satterfield, "MassTransfer in Heterogeneous Catalysis", M.I.T. Press, Massachusetts(1970)]. This invention is saliently featured by defining the size ofthe catalyst particles in relation to the pore diameter.

After examining the relation between the particle and pore diameters ofthe catalyst in connection with the decomposition of asphaltene invarious types of heavy hydrocarbon oils, the inventors of this inventionhave found that the particle diameter of the catalyst which is suitablefor this reaction, i.e., the average catalyst diameter, ACD, expressedin millimeter as hereinbefore defined must not exceed the value obtainedby the following formula:

    ACD=(APD/100).sup.0.5                                      (4)

The activity of the catalyst for asphaltene decomposition decreases asan exponential function of its particle diameter; a particle diameter inexcess of the aforementioned average catalyst diameter is too large toprovide a satisfactory level of catalytic activity. If the catalystparticles are too small, it is difficult to use them with a fixed,moving or ebullated bed, or other reaction system widely used in the artfor the catalytic hydrotreatment of a heavy hydrocarbon oil. Forinstance, various disadvantages may result from the use of too smallcatalyst particles with a fixed bed system, including an increasedpressure drop in the catalyst bed, pulverization of the catalyst duringuse, and agglomeration of the particles by deposition of heavy metalsand coke. Accordingly, if any such ordinary reaction system is employed,the catalyst is desired to have a particle diameter of about 0.6 toabout 3.0 mm, preferably about 0.6 mm to about 1.5 mm, in terms of theaverage catalyst diameter. One of the important requirements which anoptimum catalyst must satisfy from the standpoint of industrial use isthat it should have a satisfactory level of mechanical strength. Themechanical strength of a molded catalyst is generally expressed by wayof its crushing strength and abrasion loss. In order to be suitable forthe hydrotreatment of a heavy hydrocarbon oil, particularly thedecomposition of asphaltenes therein, it is preferred that the catalysthave a crushing strength of at least about 1.5 kg, more preferably atleast 2.0 kg, and an abrasion loss not greater than about 10% by weight,more preferably not greater than about 6% by weight. An optimum catalysthaving at least a required level of mechanical strength, especiallycrushing strength, has been found to require a pore volume, PV, which isnot greater than the value X' calculated according to the followingequation: ##EQU7## wherein ln is a symbol representing a naturallogarithm. A catalyst has an extremely large abrasion loss, if its poreshaving a diameter of at least 1,500 Å have a large pore volume in total.In order to reduce the abrasion loss to a desirable level, it ispreferable to decrease the pores having a diameter of at least 1,500 Åto the extent that their total volume may be reduced to a level notgreater than about 0.03 cc/g. Macropores having a diameter of at least1,500 Å hardly contribute to providing any catalytic activity forasphaltene decomposition, but are only concerned with the crushing ofthe catalyst. Therefore, it is desirable to minimize such macropores.

For the purpose of this specification, the strength of a catalyst wasdetermined by applying the method according to the standard of theJapanese Association of Powder Industry [Journal of the Japanese Societyof Powder Engineering, Vol. 15, No. 4, page 213 (1978)] and the methodproposed by J. C. Dart [Chem. Engr. Progr., Vol. 71, No. 1, page 46(1975)]. More specifically, the abrasion loss of the catalyst wasdetermined by taking 100 g of a catalyst sample dried to the extent thatit did not contain more than about 2% of moisture, placing it in acylindrical covered stainless steel drum having a diameter of about 25cm and a depth of about 15 cm, and provided with an about 2 cm wide andabout 5 cm long baffle projecting from its inner wall, rotating the drumat a speed of about 60 rpm for 30 minutes to cause abrasion of thecatalyst, and measuring the amount of the powder thereby formed. Thecrushing strength of the catalyst was determined by placing a likewisepretreated or dried catalyst sample on an appropriate support,compressing the catalyst particles at a constant rate hydraulically by acylinder having a diameter of about 5 mm, and measuring the load underwhich the particles were crushed. For the purpose of this specification,the crushing strength of the catalyst was measured with respect to fiftycatalyst samples, and expressed by way of the average crushing loadtherefor.

A preferred catalyst embodying this invention may be defined by thefollowing characteristics:

Pore volume, PV, of pores having a diameter of at least 75 Å--0.5 to 1.5cc/g;

pore volume of pores having a diameter not greater than 100 Å--notgreater than 0.1 cc/g;

pore volume of pores having a diameter of 180 Å to 500 Å--at least 0.2cc/g;

pore volume of pores having a diameter of at least 1,500 Å--not greaterthan 0.03 cc/g;

surface area, SA--at least 70 m² /g; and

average catalyst diameter of the particles--0.6 to 1.5 mm.

The more preferred catalyst of this invention satisfies these physicalproperties, and is further characterized in that the ratio (Q/P) of thetotal volume of the pores having a diameter of 180 to 400 Å (Q) to thatof the pores having a diameter of 180 to 500 Å (P) is at least about0.5. With an increase in the total surface area of the pores having adiameter of 180 to 400 Å, the catalyst shows a higher activity forasphaltene decomposition, and if the pore volume of such pores (Q) isequal to, or greater than about a half of the volume of the pores havinga diameter of 180 to 500 Å (P), an increased activity of the catalystgreatly improves its working efficiency per unit volume occupiedthereby.

The carrier for the catalyst of this invention comprises one or moreinorganic oxides of at least one element selected from among theelements belonging to Groups II, III and IV of the Periodic Table.Examples of the oxide include alumina, silica, titania, boria, zirconiaand other oxides of a single element, and silica-alumina,silica-magnesia, alumina-magnesia, alumina-titania, silica-titania,alumina-boria, alumina-zirconia, silica-zirconia and other compositeoxides of more than one element. These oxides are used alone, or as amixture of two or more thereof.

One or more catalytic metal components are composited with the inorganicoxide carrier. The metal of the catalytic metal components is selectedfrom among the metals belonging to Groups VB, VIB, VIII and IB of thePeriodic Table, most preferably vanadium, molybdenum, tungsten,chromium, cobalt, nickel or copper. These catalytic metal components canbe effectively used, whether in the form of a metal, metal oxide ormetal sulfide, or alternatively, they may be partially combined with thecarrier material by ion exchange or otherwise. The catalytic metalcomponent should be present in the range of about 0.1% to about 30% byweight in terms of oxide based on the total weight of the catalyst.

The "Periodic Table" as herein referred to is one which appears on page628 of Webster's 7th New Collegiate Dictionary, G & C Merriam Company,Springfield, Mass., U.S.A. (1965).

These catalytic metal components dictate the activity of the catalystfor various reactions involved in the hydrotreatment of a heavyhydrocarbon oil, such as the decomposition and conversion of asphaltenesinto lower molecular compounds, and removal of metals, sulfur andnitrogen from asphaltenes. The selection and combination of metals maybe made as desired to suit the reaction on which stress is particularlyplaced on a case to case basis. For instance, it is effective to chooseat least one from among vanadium, molybdenum and copper, or use it incombination with at least one of cobalt, nickel, tungsten and chromium,for a catalyst which is primarily intended for the decomposition ofasphaltenes and removal of metals therefrom. If it is desired to promotethe activity of the catalyst for desulfurization, as well as for thosereactions, it is recommended to use a combination of, for example,cobalt and molybdenum; nickel, cobalt and molybdenum; vanadium, cobaltand molybdenum; or vanadium, nickel, cobalt and molybdenum. In the eventonly the decomposition of asphaltenes and removal of metals therefromare of interest, it may be sufficient to use one or both of vanadium andmolybdenum in the quantity of about 0.1% to about 10% weight in terms ofoxide based on the total weight of the catalyst.

Description will now be made in detail of the manufacture of thecatalyst according to this invention.

A variety of methods have hitherto been proposed for manufacturing acatalyst for hydrotreating heavy hydrocarbon oils which includes acarrier composed of at least one member selected from oxides of theelements belonging to Groups II, III and IV of the Periodic Table. Theyare, for example, set forth in detail in The Japanese Catalyst Society,"Handbook of Catalysts", Chijin Shokan (1967); B. Belmon et al.,"Preparation of Catalyst", Vol. 1 (1976) and Vol. II (1979), ElsevierScientific Publishing Company, New York; R. J. Peterson, "HydrogenationCatalysts", Noyes Data Corporation, New Jersey (1977); and M. W. Ranney,"Desulfurization of Petroleum", Noyes Data Corporation, New Jersey(1975).

As already stated, the catalyst of this invention is featured by havinga specific pore structure, particularly specific ranges of average porediameter, pore volume and pore distribution, selected so as to providethe optimum catalytic activity, stability and strength. Accordingly, amethod for preparing the catalyst according to this invention mustinclude the step of controlling the pore structure of the catalyst tothe specific one. In order to control the average pore diameter of aporous catalyst carrier composed of an inorganic oxide, it is generallyknown to control the size of the basic particles of the oxide, therebycontrolling the size of the pores formed among the particles. If thismethod were to be applied for the preparation of a catalyst having arelatively large average pore diameter as is the case with the catalystof this invention, it would be imperative to enlarge the basic particlesof the carrier oxide, resulting disadvantageously in an extremely greatreduction of the total surface area of the carrier. In order to overcomethis disadvantage, and maintain a large surface area for the carrier,while controlling the average pore diameter, it has been proposed tocontrol in various ways the shrinkage of the gel structure during theprocess of drying and calcining the hydrogel of the carrier oxide. Inconnection with these methods, however, it is to be noted that ascarriers having a substantially equal surface area can be obtained, thecontrol of the average pore diameter does not mean anything but thecontrol of the pore volume. The shrinkage of the gel structure of thehydrogel forming the carrier can, for example, be controlled by varyingthe drying speed for the hydrogel (J. Polymer Science, Vol. 34, page129), or by applying a shearing force to a thick hydrogel (JapaneseLaid-Open Patent Application No. 31597/1974). These methods are,however, capable of controlling the pore volume only within a verynarrow range, and are not desirable for the preparation of the catalystaccording to this invention.

There have been proposed a number of methods which can be employed inthe preparation of the catalyst according to this invention. Forexample, a water soluble high molecular compound, such as polyethyleneglycol, is added to the hydrogel in order to control the pore volumewithin a wide range as disclosed in Japanese Laid-Open PatentApplication Nos. 50637/1977, 104498/1977 and 104493/1979, or a part orsubstantially all of the water in the hydrogel is replaced with alcoholor the like as disclosed in Japanese Laid-Open Patent Application Nos.123588/1975 and 4093/1976. The former method is intended for varying thepore volume by varying the quantity of the high molecular compound to beadded, and preventing dense cohesion of fine hydrogel particles. Thelatter method controls the pore volume of the carrier by varying theamount of alcohol replacement to thereby change the surface tension ofwater to control the cohesion of hydrogel particles. Although thecatalyst of this invention can be prepared by either of these twomethods, neither of them is very desirable for the preparation of thecatalyst according to this invention, since they both produced onlyexpensive catalysts, and involve complicated processes. For instance,they are economically not desirable, since they finally require removalof the cohesion inhibitor by combustion, and it is also difficult toprevent the surface area reduction which may result during thecalcination of the catalyst. The latter method requires an apparatus forrecovering alcohol, and only produces a carrier which is inferior inwater resisting property, and likely to break upon absorbing water. Inaddition, it is known to prepare molded catalyst by uniting a powderedinorganic oxide, or a xerogel thereof with a specific bonding agent oradhesive, as disclosed in Japanese Patent Publication Nos. 37517/1974and 1677/1979, and Japanese Laid-Open Patent Application Nos. 55791/1976and 125192/1979. This method does not only require the use of a specialadditive as has been the case with the aforementioned methods, but isalso likely to produce a carrier having a double peaked poredistribution in which both small and large pores coexist. Thus, it isbasically not suitable for the preparation of the catalyst according tothis invention.

In view of the aforementioned problems heretofore involved in themanufacture of catalysts, the inventors of this invention have conductedextensive research to develop a method which can easily be applied forthe preparation of the catalyst according to this invention withoutusing any special additive such as the cohesion inhibitor required inthe prior art, or any particularly complicated process, and havesucceeded in developing a method which can very advantageously beemployed for the purpose intended.

The method comprises adding to a seed hydrosol of at least one memberselected from hydroxides of the elements belonging to Groups II, III andIV of the Periodic Table, while changing the pH value of the hydrosol toa hydrosol-dissolution region and to a hydrosol-precipitation regionalternately, at least one hydrosol forming substance containing anelement selected from the elements belonging to Groups II, III and IV ofthe Periodic Table during the change in the pH value to at least oneside of the regions, thereby effecting growth of a crystallite of theseed hydrosol to a coarse aggregate hydrogel from which the carrier isprepared. Each of the steps of changing the pH value of the hydrosol tothe dissolution region and changing the pH value to the precipitationregion is performed at least one time, preferably 2 to 50 times.

The hydrosol forming substance is an element selected from among theelements belonging to Groups II, III and IV of the Periodic Table, or acompound thereof. Examples of preferred hydrosol forming substanceinclude magnesium, boron, aluminum, silicon, titanium, zirconium,compounds thereof and mixtures thereof.

Specific examples of the hydrosol forming substance include magnesiumcompounds, such as magnesium hydroxide, Mg(OH)₂ ; magnesium oxide, MgO;magnesium carbonate, MgCO₃ or MgCO₃.3H₂ O; magnesium nitrate,Mg(NO₃)₂.6H₂ O; magnesium chloride, MgCl₂.6H₂ O; and magnesium sulfate,MgSO₄.7H₂ O. They also include boron compounds, such as boric acid, H₃BO₃ ; ammonium borate, NH₄ B₅ O₈.4H₂ O; sodium borate, Na₂ B₄ O₇.10H₂ O;and sodium perborate, NaBO₃.4H₂ O. Also included as preferred startingmaterials are metallic aluminum, Al; and aluminum compounds, such asaluminum chloride, AlCl₃ or AlCl₃.6H₂ O; aluminum nitrate, Al(NO₃)₃.9H₂O; aluminum sulfate, Al₂ (SO₄)₃ or Al₂ (SO₄)₃.18H₂ O; polyaluminumchloride, [Al₂ (OH)_(n) --Cl_(6-n) ]_(m) (1<n<5, and m<10); ammoniumalum, (NH₄)₂ SO₄.Al₂ (SO₄)₃.24H₂ O; sodium aluminate, NaAlO₂ ; potassiumaluminate, KAlO.sub. 2 ; aluminum isopropoxide, Al[OCH(CH₃)₂ ]₃ ;aluminum ethoxide, Al(OC₂ H₅)₃ ; aluminum t-butoxide, Al[OC(CH₃)₃ ]₃ ;and aluminum hydroxide, Al(OH)₃. Particularly preferable are aluminumsalts, such as aluminum chloride, AlCl₃ or AlCl₃.6H₂ O; aluminumnitrate, Al(NO₃)₃.9H₂ O; and aluminum sulfate, Al₂ (SO₄)₃ ; andaluminates, such sodium aluminate, NaAlO₂ ; and aluminum hydroxide,Al(OH)₃. Preferred materials involving silicon include ultrafine-grainedanhydrous silica (SiO₂) or colloidal silica (SiO₂.XH₂ O), which is acolloidal solution of ultrafine particles of silicon oxide, or silicicacid anhydride; sodium silicate, Na₂ O.XSiO₂.YH₂ O (x=1 to 4); silicontetrachloride, SiCl₄ ; and silicic acid ester, Si(OCH₃)₄ or Si(OC₂ H₅)₄.Particularly preferred are colloidal silica, and sodium silicate.Preferred materials involving titanium are, for example, orthotitanicacid, H₄ TiO₄ ; metatitanic acid, H₂ TiO₃ ; titanium oxide, TiO₂ ;titanium chloride, TiCl₃ or TiCl₄ ; titanium sulfate, Ti₂ (SO₄)₃ orTi(SO₄)₂ ; titanium oxysulfate, TiOSO₄ ; titanium bromide, TiBr₄ ;titanium fluoride, TiF₃ or TiF₄ ; and titanic acid ester, Ti[O.CH(CH₃)₂]₄. Examples of preferred materials involving zirconium are zirconylchloride, ZrOCl₂.8H₂ O; zirconyl hydroxide, ZrO(OH)₂ ; zirconyl sulfate,ZrO(SO₄); sodium zirconyl sulfate, ZrO(SO₄).Na₂ SO₄ ; zirconylcarbonate, ZrO(CO₃); ammonium zirconyl carbonate, (NH₄)₂ ZrO(CO₃)₂ ;zirconyl nitrate, ZrO(NO₃)₂ ; zirconyl acetate, ZrO(C₂ H₃ O₂)₂ ;ammonium zirconyl acetate, (NH₄)₂ ZrO(C₂ H₃ O₂)₃ ; zirconyl phosphate,ZrO(HPO₄)₂ ; zirconium tetrachloride, ZrCl₄ ; zirconium silicate, ZrSiO₄; and zirconium oxide, ZrO₂.

The preferred hydrosol forming substances for the preparation of acatalyst according to this invention are those which ultimately give aporous inorganic oxide carrier, such as alumina, silica, magnesia,titania, boria, zirconia, silica-alumina, silica-magnesia,silica-titania, silica-zirconia, alumina-magnesia, alumina-titania,alumina-boria and alumina-zirconia.

The preparation of a catalyst according to this invention will now bedescribed in further detail.

(1) Formation of a Seed Hydrosol

According to this invention, a seed hydrosol formed of at least onemember selected from hydroxides of the elements belonging to Groups II,III and IV of the Periodic Table is first established. The seed hydrosolcan be prepared by any known method, such as by heterogeneousprecipitation, homogeneous precipitation, coprecipitation, ion exchange,hydrolysis and metal dissolution using as starting material at least oneof the above-mentioned hydrosol forming substances. It it is desired toobtain larger seed hydrosol particles, it is sufficient to age orhydrothermally treat the seed hydrosol obtained by any of theaforementioned methods.

Heterogeneous precipitation is a method in which an alkaline or acidicsolution of a hydrosol forming substance is neutralized with a solutioncontaining an acid or alkaline salt. For example, ammonia, sodiumhydroxide, or the like is added as a neutralizing agent into a solutionof a hydrosol forming substance in the form of a nitrate or sulfate,while it is being stirred; or a solution of a hydrosol forming substancein the form of an alkali metal salt or an ammonium salt is neutralizedwith hydrochloric or sulfuric acid, and converted to a hydroxide. Aspecific example of such heterogeneous precipitation comprises addingammonia or sodium hydroxide into a solution containing aluminum nitrate,magnesium nitrate or titanium sulfate as a neutralizing agent, while itis being stirred, thereby forming a seed hydrosol of alumina, magnesiaor titania.

Homogeneous precipitation is basically the same as heterogeneousprecipitation, but is distinguished from it by maintaining theconcentration of the neutralizing agent uniform throughoutneutralization to ensure uniform precipitation. For example, homogeneousprecipitation from a solution containing a hydrosol forming substance inthe form of an acid salt employs an ammonia releasing substance, e.g.,urea or hexamethylenetetramine, as a neutralizing agent. A specificexample of homogeneous precipitation comprises dissolving a necessaryquantity of urea in an aluminum nitrate solution, heating the resultingmixed solution gradually while stirring it, whereby decomposing theneutralizing agent gradually to cause it to release ammonia, andneutralizing the aluminum nitrate with the released ammonia gradually toconvert it to a seed alumina hydrosol.

Coprecipitation is a method for preparing a hydrosol by neutralizingsimultaneously at least two acidic or alkaline hydrosol formingsubstances together, or neutralizing a mixture of at least one acidichydrosol forming substance and at least one alkaline hydrosol formingsubstance. A specific example of this method comprises adding sodiumhydroxide as a neutralizing agent into a mixed solution containing bothaluminum nitrate and magnesium nitrate, while stirring it, therebyforming a coprecipitated seed hydrosol of alumina and magnesia; oradding a magnesium nitrate solution into a sodium aluminate solution forneutralization, while stirring it, whereby a coprecipitated seedhydrosol of aluminamagnesia is formed.

The ion exchange method forms a colloidal sol by exchanging with an ionexchange resin cations or anions coexisting in a solution containing ahydrosol forming substance. A specific example of this method comprisespassing a dilute solution of sodium silicate through a cation exchangeresin, and heating the resulting solution to polymerize the silicaparticles therein, thereby forming a colloidal silica sol. Commerciallyavailable colloidal silica or alumina is usually prepared in this way.

The method involving hydrolysis forms a hydrosol by adding water into ahydrolyzable hydrosol forming substance to effect its hydrolysis. Aspecific example of this method comprises adding an alcoholic solutionof titanium tetrachloride or aluminum isopropoxide gradually into water,while stirring it, to effect its hydrolysis, whereby a seed titaniahydrosol or alumina hydrosol is formed.

The method involving metal dissolution employs an alkaline substanceformed by dissolution of a metal, as a neutralizing agent for an acidichydrosol forming substance. A specific example of this method compriseskeeping an aluminum nitrate solution boiling, and adding metallicaluminum powder gradually into the solution to dissolve it therein,whereby aluminum hydroxide is formed and acts as a neutralizing agent toform a seed alumina hydrosol.

The properties, or crystal size or condition of the hydrosol particlesthus formed can be modified appropriately, for example, by aging orhydrothermal treatment. For example, an alumina hydrosol can have itsparticles enlarged by aging, and if the aging treatment is conductedunder heat, there are formed particles enlarged by the progress ofpseudo-boehmitization. If the pseudo-boehmitized hydrosol particles aretreated hydrothermally at a temperature of 100° C. to 300° C., there areobtained hydrosol particles having a boehmite crystal form. If thedegree of this hydrothermal treatment is controlled appropriately, it ispossible to vary the size of the particles in the range of about 50 Å toabout 5,000 Å. The crystal growth of the hydrosol particles can beeasily controlled, if the hydrothermal treatment is performed in thepresence of chromic, tungstic or molybdic acid ions. If a hydrosolcomposed of magnesium hydroxide particles is aged under heat for severalhours, it is possible to increase its stability in water several times.If a hydrosol of titanium hydroxide particles is aged under boiling forat least one hour, its crystal form can be changed from the α- toβ-form.

For the manufacture of a catalyst according to this invention, it ispreferable to prepare a seed hydrosol as described below:

An aqueous solution of aluminum salt is maintained at a temperature ofat least 70° C., and an acid or alkaline solution is added into thealuminum salt solution to adjust its pH value to 6-11, thereby forming aseed alumina hydrosol, and additionally if desired, the hydrosol is agedat 70° C. or above for 0.5 hour;

An aluminum salt or an aqueous solution thereof is neutralized to forman alumina hydrosol, and the hydrosol is hydrothermally treated at atemperature of about 100° C. to about 300° C. for about 0.5 to 24 hours,by adding chromic, tungstic or molybdic acid ions if desired;

An aqueous solution of sodium silicate containing 1 to 8% by weight ofsilica is maintained at a temperature of 10° C. to 70° C., and an acidis added thereinto to adjust its pH to a value ranging from 6 to 10,whereby a silica hydrosol is formed, and if desired, the hydrosol isaged at a temperature of 10° C. to 100° C. for 0.5 to 24 hours;

An aqueous solution of a titanium salt is maintained at a temperature of10° C. to 100° C., and an alkaline solution is added thereinto to adjustit to pH 4 to 11, or alternatively, a titanium salt or an aqueoussolution thereof is gradually added into water at room temperature forthe hydrolysis of the titanium salt, whereby a titania hydrosol isformed, and if desired, the hydrosol is aged at a temperature of 50° C.to 100° C. for 0.5 to 24 hours;

An aqueous solution of a zirconium salt is maintained at a temperatureof 10° C. to 100° C., and an alkaline solution is added thereinto toadjust it to pH 4 to 11, or alternatively, a zirconium salt or anaqueous solution thereof is added gradually thereinto for the hydrolysisof the zirconium salt, whereby a zirconia hydrosol is formed, and ifdesired, the hydrosol is aged at a temperature of 50° C. to 100° C. for0.5 to 24 hours; or

An aqueous solution of an acidic magnesium salt is maintained at atemperature of 10° C. to 100° C., and an alkaline solution is addedthereinto to adjust it to pH 6 to 11, whereby a magnesia hydrosol isformed, and if desired, the hydrosol is aged at a temperature of 50° C.to 100° C. for 0.5 to 24 hours.

As described above, various methods are known for preparing seedhydrosols, and modifying them. In this connection, it is to be notedthat as the preparation of those seed hydrosols is a matter well knownto the art, nothing connected therewith imposes any limitation on themethod of preparing a catalyst according to this invention. Thepreparation of the seed hydrosol may be carried out appropriately tosuit the type of the hydrosol forming substance to be used as thestarting material for the seed hydrosol, and the intended physicalproperties of the catalyst to be prepared. A commercially availablehydrosol may be employed, if appropriate. There is no limitation inparticular to the hydrosol concentration, unless it has undergone totalgelation to the extent that it cannot be stirred. Usually, however, itsconcentration is not greater than 10% by weight, particularly about 0.1to 5.0% by weight.

(2) Growth of Seed Hydrosol to a Hydrogel

The method of preparing a catalyst according to this invention issaliently featured by including a step for homogeneous growth of theseed hydrosol, as this step enables the industrial manufacture of thecatalysts having the physical properties intended by this invention.

During this step, the pH of the seed hydrosol is changed between adissolution region (or a first pH region) where fine hydrosol particlesare dissolved, and a precipitation region (or a second pH region) wherethe dissolved hydrosol is precipitated, by alternately adding first andsecond pH controlling agents. At least one of the first and second pHcontrolling agents includes the aforementioned hydrosol formingsubstance or substances so that ultimately, the size of the seedhydrosol particles increases uniformly. When the pH of the hydrosol isin the precipitation region, fine hydrosol particles dissolved in thedissolution region and the hydrosol formed from the hydrosol formingsubstance deposit on the undissolved hydrosol, whereby the hydratedoxide crystallites are allowed to grow. On the other hand, when the pHof the hydrosol is in the dissolution region, fine crystallites of thehydrosol are dissolved so that there remains only seed hydrosol having acertain level of sizes.

Such pH variation is effected by using a pH controlling agent. As the pHadjusting agent, it is advantageous to use the hydrosol formingsubstance per se. If the hydrosol forming substance is an acidsubstance, it acts as a pH controlling agent for lowering the pH of thehydrosol, while an alkaline hydrosol forming substance can be used toraise it. If the hydrosol forming substance is neutral, or if thehydrosol forming substance alone is not sufficient to provide asatisfactory pH control for the hydrosol, another suitable acidic oralkaline material may be used for the pH control. If an acidic materialis required, both organic and inorganic acids can be used, and include,for example, nitric acid (HNO₃), hydrochloric acid (HCl), sulfuric acid(H₂ SO₄), carbonic acid (H₂ CO₃), formic acid (HCOOH), and acetic acid(CH₃ COOH). Examples of suitable alkaline substances include ammonia(NH₃), sodium hydroxide (NaOH), potassium hydroxide (KOH), sodiumcarbonate (Na₂ CO₃, Na₂ CO₃.H₂ O, Na₂ CO₃.7H₂ O or Na₂ CO₃.10H₂ O),potassium carbonate (K₂ CO₃ or K₂ CO₃.1.5H₂ O), sodium hydrogencarbonate(NaHCO₃), potassium hydrogencarbonate (K₂ HCO₃), potassium sodiumhydrogencarbonate (KNaCO₃.6H₂ O) sodium aluminate (NaAlO₂). Thus, when,for example, the dissolution and precipitation regions are acidic andalkaline pH regions, respectively, an acidic hydrosol forming substancealone, an acidic material alone or a combination of a neutral or acidichydrosol forming substance and an acidic material can be used as thefirst pH controlling agent for adjusting the pH of the hydrosol to thedissolution region, while an alkaline hydrogel forming substance alone,an alkaline material alone or a combination of a neutral or alkalinehydrosol forming substance and an alkaline material may be employed asthe second pH controlling agent for adjusting the pH of the hydrosol tothe precipitation region. A suitable combination may be selected inaccordance with the sol intended. When the pH controlling agent is acombination of a hydrosol forming substance and an acidic or alkalinematerial, the hydrosol forming substance may be added before,simultaneously with, or after the addition of the acidic or alkalinematerial.

The method of this invention includes a cycle of the sequential steps ofchanging the pH of the hydrosol from the precipitation region to thedissolution region and bringing it back to the precipitation region toeffect the crystal growth of the seed hydrosol to a coarse mass ofhydrogel particles having an ultimately uniform size. According to thisinvention, the porous structure of the catalyst to be prepared dependson how often such cyclic pH variation is repeated. The number of timesof the cycle of the sequential steps may be only once, but is usuallyfrom twice to fifty times. The quantity of the hydrosol formingsubstance added every time is so controlled as to ensure maintenance ofa uniformly agitated condition in the reaction vessel, so that a uniformhydrosol particle dispersion may be established. If the concentration ofthe hydrosol particles is too high, it is difficult to stir the hydrosoluniformly, resulting undesirably in the occurrence of differences in thehydrosol concentration from one place to another, which may prevent theuniform growth of the hydrosol particles. The quantity of the hydrosolforming substance added every time may generally be expressed by way ofthe quantity of an oxide thereof, and ranges from 2 to 200 mol % of thetotal amount, in terms of oxide, of the seed hydrosol and the hydrosolforming substance which has been added to the seed hydrosol, i.e. thetotal amount of the hydrosol present at each time of addition of thehydrosol forming substance. The total quantity of the hydrosol formingsubstance added throughout this hydrosol growing stage is so determinedthat the hydrosol to be ultimately formed may contain about 1 to 10% byweight of hydrosol particles in terms of the weight of an oxide thereof.The quantity of the hydrosol forming substance to be added in each pHvariation is preferably the same, but may be variable in the range of-75% to 400% by weight relative to the average quantity through all thevariation steps. The hydrosol forming substance is added into thehydrosol in a form which is easily soluble therein, for example, in theform of fine powder or a solution. In the event the hydrosol formingsubstance is added in the form of an aqueous solution thereof, it has aconcentration of 0.05 to 5% by weight, preferably 0.1 to 3% by weight,in terms of the weight of an oxide thereof.

The reaction for the growth of the seed hydrosol particles is caused totake place with agitation. This agitation is conducted to ensure thatthe concentration of the hydrosol particles in the reaction vessel mayhave as uniform a distribution as possible in order to achieve theuniform growth of the hydrosol particles and to prevent fine hydrosolparticles from staying in the hydrosol without being adsorbed by largerparticles. In order to attain these objects successfully, it ispreferable to carry out the agitation as quickly as possible. Thehydrosol is maintained in the dissolution region for a sufficient timeto ensure that new fine hydrosol particles formed by each addition ofthe hydrosol forming substance be completely dissolved to form ahydrosol having a uniform particle size. If the hydrosol is left in thedissolution region for an unnecessarily long time, its particles aredissolved to an unnecessary extent, and their crystal growth isseriously inhibited. The length of this holding time is closely relatedto the value of pH of the dissolution region and the type of thehydrosol, and is desired to be selected appropriately to suit them. Theholding time may usually be in the range of about one to sixty minutesafter addition of the first pH controlling agent. It should be shortenedwith a decrease in the value of pH if the pH of the dissolution regionis on the acid side, and with an increase in the pH value if thedissolution region is on the alkaline side. For example, a hydrosol ofalumina has a pH range of 5 to 2, and the holding time therefor mayapproximately be from one to thirty minutes. A catalyst prepared from ahydrosol having an uneven particle size is inappropriate for thehydrotreatment of a heavy hydrocarbon oil, since it has its specificsurface area reduced by sintering of fine particles during itscalcination and is formed with many fine pores. If the hydrosol is heldappropriately in the dissolution region, its particles are made uniformin size.

The hydrosol may be held in the precipitation region after addition ofthe second pH controlling agent for a period of time sufficient toensure that the hydrosol formed from the hydrosol forming substance andthe dissolved fine hydrosol particles be occluded by the seed hydrosolparticles unified in size during the dissolution region to cause newcrystal growth of the hydrosol particles, and that the growth of thosecrystal particles be stabilized. This holding time is usually longerthan that for the dissolution region, and may approximately range fromone minute to ten hours. For alumina, the holding time may approximatelybe from one minute to ten hours with a pH range of 9 to 11, and forsilica-alumina, it may approximately be from one minute to ten hourswith a pH range of 6 to 11.

As is obvious from the foregoing, the pH of the hydrosol provides aguideline for the holding thereof in the dissociation or precipitationregion, and its magnitude has a very great bearing on the rates ofhydrosol dissolution and precipitation. It is a very important factor,since it also sometimes influences the crystal form of hydrosolparticles growing while the hydrosol is in the precipitation region.

The pH range differs with the type of the hydrosol forming substanceemployed, the pH controlling agent, their combination, the proportionsof the components in case of a multi-component hydrosol, the type of theparticles in a hydrosol slurry, their crystal form and concentration,the slurry temperature, the type of the salt present in the slurry ifany, or the like, but generally, the precipitation region has a pH of7±5, while the remaining acidic or alkaline range represents thedissolution range. For example, the precipitation region for an aluminahydrosol generally has a pH of 6 to 12, while its dissolution region hasa pH value less than 6 or greater than 12. For the purpose of thisinvention, however, it is desirable to vary the pH value of an aluminahydrosol between the dissolution region of pH 5 or below and theprecipitation region of pH 6 to 11. For a silica hydrosol, itsprecipitation region has a pH less than 9, and its dissolution region apH of 9 or above. A titania hydrosol has its dissolution region at lessthan pH 1.5, and its precipitation region at pH 1.5 or above. A magnesiahydrosol has its dissolution region at less than pH 9, and itsprecipitation region at pH 9 or above. A zirconia hydrosol has itsdissolution region at less than pH 2, and its precipitation region at pH2 or above. For a hydrosol composed of a composite oxide, such assilica-alumina, magnesia-alumina, silica-magnesia and alumina-titania,its dissolution and precipitation regions differ from those for itsindividual components, but depend on the proportions of its components,temperature, or the like. These pH ranges can be easily determined bysimple preliminary tests, and selected appropriately based on theresults thereof. It is also possible to obtain any intended mixedhydrosol ultimately merely by effecting the pH variation in thedissolution and precipitation regions for one of the components. Analumina-silica hydrosol has its dissolution region in the vicinity of apH value less than 6, or pH 9 or above, and its precipitation region inthe vicinity of pH 6 to 9, though strictly, these pH ranges must beselected to suit the proportions of its components, and other factors ona case to case basis.

A composite oxide hydrogel may be prepared by using as seed hydrosol amixed hydrosol composed of a mixture of the hydrosol forming substancescontaining all the elements required for the intended composite oxide,or a hydrosol containing one of the components of the mixed hydrosol.For example, a silica-alumina hydrogel can be obtained from a mixedhydrosol containing silicon and aluminum as a seed hydrosol by addingthereto alternately an acidic pH controlling agent including a mixedhydrosol forming substance containing silicon and aluminum, and anappropriate alkaline material, or alternatively, by using a seedhydrosol containing only aluminum, and adding thereto alternately anacidic pH controlling agent including an alumina hydrosol formingsubstance, and an alkaline pH controlling agent including a silicahydrosol forming substance. As a further alternative, the mixed hydrogelcan also be prepared by using a silica hydrosol as a seed hydrosol.

The temperature of a hydrosol is a factor which influences the rates ofdissolution and formation of hydrosol particles. It also influences thecrystal form of hydrogel particles growing in the precipitation region,as the pH value does. In the case of alumina, for example, there isformed amorphous aluminum hydroxide at room temperature, andpseudoboehmite at a temperature of 50° C. or above. A silica-aluminahydrogel is amorphous in the vicinity of room temperature. Magnesia isin the form of magnesium hydroxide which is stable in water at 50° C. orabove. Titania forms β-titanic acid at 80° C. or above.

The type and quantity of the ions present in the hydrosol also influencethe crystal growth of hydrosol particles, and are desired to beappropriately controlled. Particularly, polyvalent anions are likely toinhibit the crystal growth, and are desired to be reduced to 30% byweight or less, preferably 15% by weight or less.

When the hydrosol is placed in the final precipitation range after therepeated pH variation, it is precipitated as a hydrogel. The hydrogelmay be aged in the aging process to be hereinafter described.

The aforementioned operating conditions may be appropriately selected tosuit the type of the hydrogel to be prepared, and the ultimate catalyststructure intended. The selection of these conditions would be obviousto one of ordinary skill in the art of hydrotreating catalysts from theforegoing disclosure.

For the purpose of this invention, the hydrosol means a uniformdispersion in water of particles of a hydroxide of at least one elementselected from among the elements belonging to Groups II, III and IV ofthe Periodic Table, used for forming the carrier, i.e., hydrosolparticles, and in which the water forms a continuous phase in which theparticles can freely move. It is usually a colloidal milky liquid. Thehydrogel is a substance formed by precipitation of hydrosol particles,and in which the particles contact one another and cannot move freelyany longer. It is usually a gel-like solid. The dissolution region for ahydrosol mean a pH range in which, when a hydrosol forming substance hasbeen added into the hydrosol, the substance can stay in water stably indissolved form, and in which fine hydrosol particles can be dissolved.The precipitation region for the hydrosol means a pH range in which thehydrosol forming substance and the dissolved fine hydrosol particles canno longer stay stably in dissolved form in water, but are precipitated.

(3) Aging of a Hydrogel

The aging of a hydrogel is optionally carried out and can be consideredas the final step of the aforementioned hydrosol growing stage. Itcomprises holding the grown hydrogel in the hydrosol precipitationregion for a certain length of time, whereby the hydrosol particles areunified in size, and stabilized. The effect of the aging can be enhancedby stirring, and aging under heat is particularly desirable, since it islikely to stabilize the crystal form of the hydrosol particles. Aging isgenerally conducted at a temperature from ambient to 100° C., and if itis performed at a temperature above 100° C., it is carried out underpressure. The aging time is approximately in the range from 0.5 to 24hours. The hydrogel does not always need to be aged, but may betransferred to the following process without undergoing any agingtreatment.

(4) Washing of the Hydrogel

The grown hydrogel is washed, if required, for removing any unnecessaryions or impurities. Washing is usually performed once, or repeated aplurality of times, alternately with filtration. Water is usually usedas a washing medium. The washing of the hydrogel removes sodium, iron,sulfuric acid radicals, and any other component that may poison thecatalyst or reduce its strength, to the extent that their presence isnot detrimental any more. In order to increase the washing effect, it ispossible to add into the washing medium an acidic or alkaline substancewhich can be decomposed and removed during the later precalcining orcalcining process, such as ammonia, nitric acid, ammonia nitrate andammonium chloride, and to control its pH value in a suitable range,whereby the poisonous or impure matter can be rendered more soluble inthe washing medium. In order to improve the solubility of such impurematter in the washing medium, it is also useful to raise the temperatureof the washing medium, since it reduces the surface tension of the waterand increases the rate of filtration, whereby its washing efficiency isimproved. The washing of the hydrogel is preferably continued until itsimpurity content is minimized, and generally until, for example, sodiumas Na₂ O has been reduced to 0.2% by weight or less, iron as Fe to 0.2%by weight or less, and sulfuric acid radicals to 4.0% by weight or less.Silica should preferably be reduced to 2.0% by weight or less in theform of SiO₂, if any such silica is present as impure matter. Thewashing or cleaning of the hydrogel may be carried out by using acustomary apparatus, such as an atmospheric, vacuum or pressurefiltration machine, and a centrifugal separator.

When the sequential pH variation steps are repeated many times, thewashing step may additionally be conducted in the midst of the hydrosolgrowing stage.

(5) Control of Solids in the Hydrogel

The solids content of the hydrogel is controlled in the range of about10 to 80% by weight, preferably 15 to 65% by weight to facilitate itsmolding. If its solid content is less than about 10% by weight, it isdifficult to maintain a shape molded from the hydrogel, while any solidcontent in excess of about 80% by weight requires an extremely highmolding pressure, and also results in the formation of a catalystfailing to possess any satisfactory physical property. The adjusting ofthe solids content of the hydrogel may be carried out by dehydration bydrying under heat, spray drying, atmospheric, vacuum or pressurefiltration, centrifugal separation, or otherwise until a desired solidscontent is reached.

(6) Molding of the Hydrogel

The hydogel, of which the solids content has thus been adjusted ismolded into a shape which is suitable for the purpose for which thecatalyst is intended. The shape may be circular, cylindrical, whethersolid or hollow, or non-circular in cross section, e.g., oval, tri-lobor quadri-lob. The hydrogel may also be molded into a granular form. Themolding of the hydrogel may be appropriately carried out by extrusionmolding with a piston or screw type extruder, or by tablet formationwith a press or the like. The formation of the hydrogel into granulesmay be performed by, for example, oil dropping and wet granulation.

(7) Drying and Precalcination of Molded Hydrogel Products

The hydrogel product which has been molded into the desired shape anddimensions is dried, and precalcined if required. This is done in orderto stabilize the shape of the hydrogel molding. The precalcination ispreferably carried out at as high a temperature as practically possible,but appropriate conditions must be selected on a case to case basis,since some types of hydrogel are likely to cause sintering or crystaldeformation when calcined. Generally, the hydrogel is precalcined at300° to 1,000° C., preferably 400° to 700° C. The precalcination of thehydrogel molding is preceded by its drying or xerogelation. The hydrogelmolding is air dried, or dried at a temperature of at least 100° C. Inpractice, the drying and precalcination of the hydrogel molding arecarried out by drying it with hot air and calcining it in a heatingfurnace, or placing it in a heating furnace and raising its temperaturefrom 100° C. to a level required for its calcination. This processusually requires 0.5 to 10 hours. When the hydrogel has, thus, beenheated, or calcined or fired at a high temperature, it is converted toan oxide.

(8) Supporting of Catalytic Metal Component

A catalytic metal component is supported on the dry hydrogel (xerogel)or the precalcined product thereof, if no such metal component has beenadded during the aforementioned hydrogel forming process. For thispurpose, any known starting material or method of preparing the same maybe employed, only if it is possible to disperse a predetermined quantityof such component uniformly in the catalyst. For example, the startingmaterial can be selected from among various kinds of compounds eachcontaining a single or a plurality of specific elements, and any knownmethod suiting the starting material can be used for preparing thenecessary component.

The metal of the catalytic metal component for the catalyst according tothis invention is selected from among the metals belonging to Groups VB,VIB, VIII and IB of the Periodic Table. Vanadium, chromium, molybdenum,tungsten, cobalt, nickel and copper are particularly preferred.

Examples of the molybdenum compounds for use as the material for thecatalytic metal component include oxides such as MoO₃ and MoO₂, molybdicacid and its salts such as H₂ MoO₄, H₂ MoO₃ H₂ O, (NH₄)--Mo₂ O₇, (NH₄)₂MoO₄ and (NH₄)₆ Mo₇ O₂₄.4H₂ O, and chlorides such as MoCl₃ and MoCl₄.Examples of the relevant cobalt compounds include oxides such as CoO,Co₂ O₃, CoO₂ and Co₃ O₄, cobalt salts such as CoCl₂, CoCl₂.6H₂ O,Co(NO₃)₂.6H₂ O, CoSO₄.7H₂ O, Co(CH₃ CO₂)₂. 4H₂ O and CoC₂ O₄.2H₂ O,cobalt hydroxide Co(OH)₂, and cobalt carbonate (basic). Examples of therelevant nickel compounds are nickel oxide, NiO; nickel salts such asNiCl₂, NiBr₂ NiI₂ and the hydrates thereof, Ni(NO₃)₂.6H₂ O, NiSO₄.6H₂ O,Ni(CH₃ CO₂)₂.4H₂ O and NiC₂ O₄.2H₂ O; nickel hydroxide, Ni(OH)₂ ; nickelcarbonate; and nickel acetylacetonato. Examples of the relevant tungstencompounds include oxides such as WO₃ and WO₂ ; and tungstic acid and itssalts such as ammonium paratungstate and ammonium metatungstate. Therelevant copper compounds are, for example, copper nitrate, copperchloride, copper acetate and copper sulfate.

Various methods are available for supporting these catalytic metalcomponents on the carrier prepared as hereinbefore described. Forexample, predetermined quantities of cobalt and molybdenum arepreferably supported on the dried or precalcined hydrogel byimpregnating the latter with an ammoniac aqueous solution of cobaltnitrate and ammonium molybdate. It is, however, possible to use anyother known method, e.g., mixing, impregnation, kneading, or ionexchange. Alternatively, it is possible, as stated above, to select theaforementioned hydrotreating catalytic metal compound or compoundsappropriately as required, and add them as a part of the pH controllingagent during the hydrosol growing stage. Whichever of these methods maybe adopted, there is hardly any difference in the performance of thecatalyst to be obtained, if the necessary quantity of the catalyticmetal component is supported on, or incorporated into the carrier.

Vanadium can be combined with the dried or precalcined hydrogel bycontacting the latter with a non-oily, nonhydrocarbon or polar mediumcontaining a soluble vanadium compound, so that the carrier material maycontain or support the vanadium compound, followed by sulfurization. Theterm "non-oily" as herein used refers to a medium, such as an aqueoussolution, and an alcoholic solution. Examples of the soluble vanadiumcompound include vanadyl oxalate, vanadyl sulfate, ammoniummetavanadate, acetyl-acetone vanadium, and vanadium oxide. As thesevanadium compounds are generally difficult to dissolve in water or likemedium, it is desirable to heat the medium, or acidify or alkalize it inorder to improve the solubility of the vanadium compound therein. Forexample, ammonium metavanadate has a water solubility of 0.52 g/100 g H₂O at 15° C., and 6.95 g/100 g H₂ O at 96° C., and its decompositiontakes place in the vicinity of 96° C. As the vanadium compound has sucha low solubility in water, it is desirable to add oxalic acid in orderto improve its solubility.

Vanadium can also be incorporated into the carrier by the methoddisclosed in Japanese Laid-Open Patent Publication No. 54036/1980,wherein the carrier material is contacted with a heavy hydrocarbon oilcontaining a large quantity of catalyst metals, particularly vanadiumand sulfur in a hydrogen atmosphere with a hydrogen pressure of 30 to250 atm., preferably 80 to 160 atm. at 300° C. to 500° C., preferably390° to 420° C., whereby the hydrocarbon oil is demetallized anddesulfurized, and a pedetermined quantity of sulfurized metal,particularly vanadium sulfide (VS_(x)), is deposited on the carriersurface. The heavy hydrocarbon oil used for this purpose is moreeffective if it contains more vanadium, and specifically, it isdesirable to use oil containing at least 200 ppm of vanadium, preferablyat least 400 ppm of vanadium.

In addition to the above-mentioned catalytic metal component forcatalytic hydrotreatment, it is effective to add fluorine or phosphorusto the catalyst in order to improve its activity for other specificreactions, such as denitrification and reduction of Conradson carbonresidue. These auxiliary catalytic elements can be incorporated into, orsupported on the catalyst in a quantity of about 0.2 to 4.0% by weightin a customary manner. In order to incorporate fluorine, it is possibleto add hydrogen fluoride (HF), ammonium fluoride (NH₄ F), ammoniumhydrogenfluoride (NH₄ HF₂), or the like. If phosphorus is to beincorporated, it is possible to use phosphorus oxide (P₂ O₅), phosphoricacid or a salt thereof, such as orthophosphoric acid, metaphosphoricacid, pyrophosphoric acid and ammonium phosphate, or the like. Thesefluorine or phosphorus compounds may be added with the metal componentfor hydrotreatment. In other words, it is possible to use a substancecontaining two or more catalyst forming elements, such as titaniumphosphate, phosphotungstic acid, phosphomolybdic acid and ammoniumphosphomolybdate.

Various known methods may be used for incorporating the catalytic metalcomponent or auxiliary components such as fluorine and phosphorus. See,for example, "Handbook of Catalysts", Japanese Catalyst Society,Catalyst Engineering Course, Vol. 10, Chijin Shokan (1967).

The catalytic metal component thus supported on the carrier is dried,and calcined so that it may be firmly secured to the carrier. It may bedried and calcined under the same conditions with the aforementionedprecalcination of the hydrogel. The calcination temperature isappropriately selected to suit the components forming the catalyst,since too high a temperature is likely to cause changes in the physicalproperties of the carrier material by sintering, and reduction in theactivity of the catalyst by chemical reaction between the catalyticmetal component and the carrier material. The drying and calcining stepis carried out in a temperature range of about 100° C. to about 1,000°C. as is the case with the precalcining step.

As described previously, supporting of the catalytic metal component onthe carrier material cannot only be effected after drying or calciningthe hydrogel, but can also be effected before molding the hydrogel, evenduring the growth of the hydrosol. For example, the catalytic metalcomponent may be added to the hydrosol in the form of a soluble salttogether with a pH controlling agent, or as a part thereof. The hydrogelinto which the metal component has been added is molded, formed intoxerogel and ultimately calcined, whereby to obtain a catalyst having thecatalytic metal component composited with the inorganic oxide carrier.In an alternative, the catalytic metal component may be added into thegrown hydrogel and kneaded therewith in order to incorporate the metalcomponent into the hydrogel. The hydrogel into which the metal componenthas been mixed is molded, formed into a xerogel, and calcined, wherebyit is converted to an inorganic oxide in which the metal component isdispersed.

The catalyst of this invention can be prepared industriallyadvantageously by the method as hereinabove described. It isparticularly to be noted that the specific process employed forpromoting the growth of the hydrogel makes it possible to manufacturethe catalyst having a special porous structure according to thisinvention.

By virtue of its specific porous structure, the catalyst of thisinvention provides superior results not achieved by any known catalystwhen applied for hydrotreating a heavy hydrocarbon oil containingasphaltenes. Description will now therefore be made in detail of aprocess for hydrotreating a heavy hydrocarbon oil by using the catalystof this invention.

The process for hydrotreating according to this invention includes thestep of bringing a heavy hydrocarbon oil containing asphaltenes intocontact with the catalyst of this invention under hydrotreatingconditions to cause the asphaltenes to be decomposed and converted tolower molecular compounds, and reduce the contaminants, such as heavymetals, sulfur compounds and nitrogen compounds, which the oil contains.For the purpose of this invention, therefore, the term "hydrotreatment"means treating a heavy hydrocarbon oil containing high molecularhydrocarbon fractions, such as asphaltenes, to reduce their contents byconverting them to distillable hydrocarbon fractions or hydrocarbonfractions soluble in a light hydrocarbon, and also treating the heavyhydrocarbon oil in a hydrogen atmosphere to remove or reducecontaminants, such as heavy metals, and sulfur and nitrogen compounds,therefrom.

The feedstock oil for which the hydrotreating process of this inventionis intended is a heavy hydrocarbon oil containing at least about 2% byweight, particularly at least 5% by weight, of asphaltenes, and at least50 ppm, and particularly at least 80 ppm, of heavy metals. If anasphaltic heavy hydrocarbon oil containing large quantities of vanadiumand sulfur is hydrotreated by using the novel catalyst of thisinvention, vanadium and sulfur are removed from the oil, especially fromthe asphaltenes therein, and the asphaltenes are decomposed andconverted to lower molecular compounds. The vanadium and sulfur thusremoved form vanadium sulfide (VS_(x)) and are deposited on the catalystsurface, and this compound shows activity for further demetallization,desulfurization and selective decomposition of asphaltenes. Asasphaltenes are decomposed, the catalyst has little coke depositedthereon, and can maintain a high activity for a long period of time.While such vanadium compounds in a heavy hydrocarbon oil have hithertobeen considered to poison any known hydrotreating catalyst such asNi-Co-Mo-γ alumina catalyst, it serves as an active substance VS_(x) forthe catalyst of this invention when deposited on its substrate, asdisclosed in Japanese Patent Application No. 153200/1978. Thus, thecatalyst of this invention has a very high value when put to practicaluse, as opposed to any known catalyst. The catalyst of this inventionshows unique reactions not observed with any known catalyst, such asdecomposition and conversion of asphaltenes into lower molecularcompounds, and selective demetallization and desulfurization forasphaltenes, though the mechanisms of these reactions have not yet beenfully clarified.

Asphaltenes, which are responsible for accelerating reduction in theactivity of a catalyst, are generally considered to be micellarmacromolecules formed by association of molecules of several highmolecular aromatic condensed rings and dispersed in oil in the form ofcolloid. It is also believed that vanadium plays a significant part inthe association of asphaltene molecules in such a manner that an organicvanadyl (VO) compound, or the like forms intramolecular andintermolecular complexes with asphaltene molecules, whereby theasphaltene molecules are associated with one another to form micellarmolecules. (T. F. Yen, "In Role of Trace Metals in Petroleum", AnnArbor, Mich., Ann Arbor Scientific Publishers, 1975.) It is alsounderstood that asphaltenes are high polymers composed of crosslinkedrecurring units each having an approximate molecular weight of 800 to1,200 and containing a polycyclic aromatic nucleus to which aliphaticside chains, naphthene rings, etc. are bonded, and that the crosslinkedbonds include relatively weak bonds as compared with the C--C bonds inether and thioether [see, for example, J. P. Dickie and T. F. Yen, Anal.Chem., 39, page 1,847 (1967 ); G. A. Haley, Anal. Chem., 43, page 371(1971); P. A. Witherspoon and R. S. Winniford, "Fundamental Aspects ofPetroleum Geochemistry", in B. Nagy and U. Colombo (ed), Elsevier,Amsterdam, pages 261-297 (1967); and T. Igrasiak et al., J. Org. Chem.,42, page 312 (1977)]. In view of the properties of asphaltenesheretofore reported and the aforementioned characteristics of thereactions caused by the catalyst of this invention, it is possible togive the following qualitative assumption for the mechanisms of thereactions caused by the catalyst of this invention.

When asphaltenes in a heavy hydrocarbon oil diffuse into the pores ofthe catalyst and are adsorbed by the active centers composed of thecatalytic metal components carried on the internal surface of thecatalyst, the removal of vanadium and sulfur takes place, and theintramolecular and intermolecular vanadium complexes in asphaltenes arewithdrawn, and deposited and fixed on the catalyst surface. As themicells in the asphaltenes have lost the vanadium complexes, itsmolecular association is broken and decomposed into the individualmolecules, and as the intramolecular trioether and other weak bonds inthe asphaltenes are selectively broken by desulfurization, theasphaltenes are depolymerized and their molecular weight is lowered. Asthe vanadium sulfide, VS_(x), formed during the course of the reactionis active for the decomposition of asphaltenes, the catalyst is hardlypoisoned by vanadium, but can maintain its high activity for a longperiod of time.

The porous structure of the catalyst according to this invention playsan important role in the effective hydrotreatment of a heavy hydrocarbonoil. The catalyst of this invention has a pore diameter distributionwhich permits easy diffusion of high molecular hydrocarbon compounds,such as asphaltenes, into the active sites in the pores. The pores inthe catalyst have a sufficient volume to prevent the rate of diffusionof asphaltenes from being restricted by metal sulfides (mainly vanadiumsulfide) formed during the course of the reaction and deposited in thepores. This porous structure permits the catalyst to maintain a highactivity for decomposition of asphaltenes. The catalyst of thisinvention selectively decomposes coke precursors, such as asphaltenes,and maintains a high activity without having its activity reducedappreciably by deposition of coke when applied to a mixed heavyhydrocarbon oil.

The catalyst of this invention is also very advantageous for its smallhydrogen consumption, as compared with any known hydrotreating catalyst.While the hydrocracking of a heavy hydrocarbon oil with a known hydrogentreating catalyst, such as Ni-Co-Mo-γ-alumina, mainly compriseshydrodealkylation of polycyclic aromatic compounds based on thehydrogenation and hydrocracking thereof, the hydrogen treatment by thecatalyst of this invention mainly includes removing metals fromasphaltene molecules forming micelles, thereby lowering the degree ofassociation in the micelles, and converting asphaltenes to lowermolecules by breaking their relatively weak bonds. This is considered tobe the reason for the low hydrogen consumption relative to the reductionin the molecular weight.

The catalytic hydrogen treatment of this invention may be carried out byany ordinary flow system, such as a fixed, moving, fluidized orebullated bed, without causing any catalyst to be carried out of thereaction area with the reaction product, if the shape of the catalyst,etc. are properly selected. The reactant may be fed into the reactionzone through the top or bottom of the reactor. In other words, the flowof the gas and the liquid in the reactor may be co-current upwardly ordownwardly. The catalyst particles may be granular, spherical orcylindrical, but for the hydrotreatment of a heavy hydrocarbon oilcontaining large quantities of asphaltenes and heavy metals, it isdesirable to use extrusion molded catalyst particles which are hollowcylindrical, non-circular in cross section, e.g., oval, tri-lobed ormulti-leafed, or elongated and have a surface provided with at least onegroove. When these specially shaped particles are used to form a fixedbed, they increase the voids in the reactor, and it is not only possibleto reduce the pressure drop in the catalyst bed, but the blocking of thecatalyst bed by deposition of coke and metal among the catalystparticles can also be improved remarkably.

The conditions for the hydrotreatment according to this inventioninclude a temperature of 300° C. to 500° C., preferably 370° C. to 430°C., a hydrogen pressure of 50 to 250 atm., preferably 80 to 200 atm.,and a liquid space velocity of 0.1 to 10 hours⁻¹, preferably 0.2 to 5hours⁻¹.

If the reaction temperature is below 300° C., the catalyst fails to showits full activity, and the reaction and conversion ratio in thehydrotreating process fails to reach any practically acceptable level.If it exceeds 500° C. on the other hand, asphaltenes undergopolycondensation, and tend to increase, rather than decrease. Moreover,coking occurs more actively, thereby causing degradation of the product,reduction in the activity of the catalyst and agglomeration of catalystparticles. If the hydrogen pressure is below 50 atm., coking occurs soactively that it is very difficult to maintain the activity of thecatalyst at a normal level. Any hydrogen pressure in excess of 250 atm.brings about too active hydrocracking, and is not practically acceptablefrom the economical standpoint, since there result an increased hydrogenconsumption, a reduced yield of production, and an increased cost of thereactor and other associated equipment. If the liquid space velocity isless than 0.1 hour⁻¹, a prolonged process time for oil brings aboutdegradation of the product due to the thermal change of its heavycomponents, while any velocity in excess of 10 hours⁻¹ brings about alower reaction and conversion ratio per pass which is practicallyunacceptable.

The proportion of hydrogen or a gas containing hydrogen to the feedstockoil to be fed into the reaction zone may be 100 to 2,000 volumes ofhydrogen at 15° C. per volume of the oil at 1 atm. and 15° C. (i.e., 100to 2,000 N lit./lit.), preferably 500 to 1,000 N lit./lit. If it is lessthan 100 N lit./liter, the reaction zone becomes short of hydrogen, nosufficient hydrogen is fed into the liquid, resulting in coking, whichhas an adverse effect on the properties of the catalyst and the oil tobe produced. Any proportion in excess of 2,000 N lit./liter does notprovide any additional benefit in the process of this invention, thoughit does not present any problem in the reaction. The cost of acompressor used for circulating hydrogen depends on the quantity of thehydrogen to be circulated, and is very high for supplying hydrogen inexcess of 2,000 N lit./liter. Thus, the quantity of 2,000 N lit./litermay be a practical upper limit to the circulation of hydrogen. The gaswhich is rich in hydrogen and circulated through the reaction zone maycontain hydrogen sulfide. It does not have any adverse effect, but eventends to promote the reaction if its quantity is appropriate. Thecatalyst used for the purpose of this invention has some interactionwith hydrogen sulfide under the aforementioned conditions for thereaction, and hydrogen sulfide plays a certain role in maintaining theactivity of the catalyst. The hydrogen to be fed into the reaction zonecan contain up to 10 mol % of hydrogen sulfide within the scope of thisinvention.

The reaction product obtained by the hydrotreating process under theaforementioned conditions, and not containing any catalyst is deliveredto a gas-liquid separation zone, where it is separated into a gas whichis rich in hydrogen, and a product consisting substantially solely of aliquid. Any method and apparatus used in an ordinary desulfurizationprocess with a fixed or ebullated bed may be employed for the gas-liquidseparation.

A preferred conversion ratio for asphaltenes for each pass is in therange of 40 to 90%, depending mainly on the properties of the feedstockoil to be treated, and the hydrogen consumption. An excessively highconversion ratio for each pass under severe reaction conditions does notonly result in undesirable side reactions which lower the quality of theoil to be produced, but is also disadvantageous from the economicalstandpoint with an increase in the consumption of hydrogen and catalyst.

In order to obtain oil containing a markedly reduced quantity ofasphaltenes, or a light hydrocarbon oil containing substantially noasphaltenes (hereinafter referred to simply as "light oil") at a highyield from the feedstock oil containing a large quantity of asphaltenes,it is advantageous to follow the following sequence of steps forhydrotreatment:

(a) Treating the feedstock oil under hydrotreating conditions in thepresence of the catalyst according to this invention;

(b) separating the reaction product into a hydrogen-rich gas and aliquid product;

(c) separating the liquid product into a substantially asphaltene-freeand heavy metal-free light oil fraction and a heavy fraction containingasphaltenes and heavy metals; and

(d) recycling the heavy fraction to step (a) for hydrotreatment.

This hydrotreating process involving asphaltene recycling is onlypossible with the catalyst of this invention having a superior activityfor decomposition of asphaltenes, and capable of maintaining its highselective activity in a stable manner for a heavy hydrocarbon oilcontaining a large quantity of asphaltenes. According to this process,it is possible to convert the stock oil containing a large quantity ofasphaltenes continuously to a light oil not containing asphaltenes orheavy metals. Such recycling treatment does not sharply increase thehydrogen and catalyst consumption, and raises the yield of the light oilto be produced.

This process is advantageously applicable to the feedstock oilcontaining at least 5% by weight, and particularly at least 10% byweight of asphaltenes, and at least 80 ppm, and particularly at least150 ppm of vanadium. The separating step can be accomplished by anyordinary method, such as distillation and solvent deasphalting. Theseparating operation can be carried out smoothly, as the liquid productdoes not contain substantially any solid. If the separation is conductedby solvent deasphalting, it is possible to use as a solvent at least onelow molecular hydrocarbon, such as methane, ethane, propane, butane,isobutane, pentane, isopentane, neopentane, hexane and isohexane. Thesolvent and the liquid reaction product are brought into countercurrentcontact with each other.

Solvent deasphalting may be carried out at a temperature of 10° C. to250° C., preferably 50° C. to 150° C., and a pressure of 3 to 100 atm.,preferably 10 to 50 atm. The solvent and the light oil leaving thesolvent deasphalting operation are delivered into a solvent recoveryapparatus in which the solvent is separated, and a light oil containingsubstantially no asphaltenes or heavy metals is obtained.

The heavy fraction phase obtained by the separation step containsunreacted asphaltenes and heavy metals, and is recycled to the hydrogentreating step. No special method or apparatus is required for thisrecycling transfer, since the heavy fraction phase does not contain anysolid, such as catalyst and metal sulfides. The quantity of the heavyfraction to be recycled depends on the properties of the feedstock oiland the conditions for the treatment, and while the whole fraction canbe recycled, it is also possible to omit a part thereof. It is furtherpossible to omit the whole quantity of the heavy fraction from therecycling treatment, if the hydrotreating step has a sufficiently highrate of asphaltene decomposition for each pass, the quantity of theheavy fraction is considerably small, and the yield of the light oil isnot sharply reduced.

According to the hydrotreatment employing the catalyst of thisinvention, it is possible to obtain oil having improved quality byreducing impurities, such as asphaltene and vanadium, sharply. The oilobtained has been found to have unique properties differing from thoseof the product obtained by any known method, irrespective of the type ofthe feedstock oil used. The hydrocarbon contained in the productobtained according to this invention has a molecular weight of about 200to about 1,200. The asphaltenes remaining to a slight extent in the oilproduct have a considerably lower molecular weight than that in thestock oil, and contain sharply reduced quantities of sulfur and heavymetals. A greater proportion of sulfur and nitrogen in the product ispresent in its light fraction, as opposed to their distribution in thefeedstock oil.

In view of the specific properties of the product obtained byhydrotreating the feedstock oil in the presence of the catalyst of thisinvention, the inventors of this invention have conducted extensiveresearch on hydrotreatment to obtain an oil product having a stillhigher grade, and developed a two-stage hydrotreating process having avery high industrial advantage.

The two-stage hydrotreating process of this invention comprises thefollowing steps:

(a) bringing a heavy hydrocarbon oil containing asphaltenes into contactwith the catalyst of this invention at a temperature of 300° C. to 500°C., a hydrogen pressure of 50 to 250 atm. and a liquid space velocity of0.1 to 10.0 hours⁻¹ ; and

(b) at a temperature of 300° C. to 500° C., a hydrogen pressure of 50 to250 atm. and a liquid space velocity of 0.1 to 10.0 hours⁻¹, bringing atleast a portion of the product of step (a) into contact with a catalystwhich comprises a porous carrier containing alumina and havingcomposited therewith a first catalytic metal component composed of atleast one compound selected from among the oxides and sulfides of themetals belonging to Group VIB of the Periodic Table and a secondcatalytic metal component composed of at least one compound selectedfrom among the oxides and sulfides of the metals belonging to Group VIIIof the Periodic Table, and which catalyst has, with regard to its poreshaving a diameter of 75 Å or more, the properties: an average porediameter APD of about 80 Å to about 250 Å, a pore volume PV of about 0.4cc/g to about 1.5 cc/g, and a surface area SA of about 100 m.sup. 2 /gto about 400 m² /g.

The carrier for the catalyst used in step (b) supports thereon acombination of at least one compound selected from among the oxides andsulfides of the metals belonging to Group VIB of the Periodic Table, andat least one compound selected from among the oxides and sulfides of themetals belonging to Group VIII of the Periodic Table. This combinationis preferably a combination of at least one selected from the oxides andsulfides of chromium, molybdenum and tungsten, and at least one selectedfrom among those of cobalt and nickel. The metal component preferablycontains about 2 to 40% by weight of the compound of the metal belongingto Group VIB, and about 0.1 to 10% by weight of the compound of themetal belonging to Group VIII, both in terms of the weight of the oxide,based on the total weight of the catalyst. It is desirable to use acatalyst having an average pore diameter APD of about 80 Å to 180 Å instep (b).

Step (b) is intended for removing sulfur, nitrogen, Conradson carbonresidue and residual metal. The aforementioned metal components governthe activity of the catalyst for various reactions involved in thehydrotreatment for attaining the purposes for which step (b) isintended. The selection and combination of the metal components dependon the reaction on which the utmost importance should be placed on acase to case basis. For example, a combination of molybdenum, and atleast one of cobalt, nickel, tungsten and chromium is effective forremoving sulfur and metal. A combination of cobalt and molybdenum, ornickel, cobalt and molybdenum is preferred for promoting the activity ofthe catalyst for desulfurization. In order to promote the activity fordenitrification and reduction of Conradson carbon residue, too, it isdesirable to add as an auxiliary catalyst component at least one of thecompounds of titanium, boron, phosphorous and fluorine, or boronphosphate, or boron fluoride. In this case, the catalyst can effectivelycontain about 1.0 to 30% by weight of any such auxiliary component, interms of the weight of the oxide, based on the total weight of thecatalyst. Both the catalytic metal component and the auxiliary componentcan be combined with the carrier by any ordinary method, such as mixing,immersion and spraying.

The catalyst employed for step (b) may be prepared by any known method,if there can be obtained a catalyst having a desired porous structure,particularly an average pore diameter APD of about 80 Å to 250 Å, a porevolume PV of about 0.4 to 1.5 cc/g and a surface area SA of about 100 to400 m² /g. See, for example, Japanese Patent Publications Nos.21973/1965, 20911/1971, 46268/1972, 23786/1974, 12397/1975, 38298/197610558/1977 and 36435/1978, and Japanese Laid-Open Patent ApplicationsNos. 31597/1974, 37594/1977 and 96489/1979. The method and conditions ofthe treatment for step (b), and the particle diameter and shape of thecatalyst to be employed therein may be equal to those already describedin connection with the hydrotreatment using the catalyst of thisinvention.

The two-stage hydrotreating process has a great industrial advantage,since it can remove impurities from oil very efficiently with anextremely small hydrogen and catalyst consumption as compared with theknown direct sulfurization process.

The carrier for the catalyst used for step (b) is a carrier containingat least 70% by weight of alumina, and preferably composed of aluminaalone, or silica an alumina.

The two-stage hydrotreating process of this invention is a superiorprocess which can be utilized for converting substantially the wholequantity of the feedstock heavy oil to a high grade desulfurized oil,even if it is required to treat a very bad heavy oil containing stilllarger quantities of asphaltenes and heavy metals, or even if it isrequired to conform to very stringent specifications for the product tobe obtained. The industrially advantageous two-stage treatment of anysuch bad heavy oil may be carried out by physically separating a heavyfraction containing asphaltenes or heavy metals from the product of thefirst step, and recycling it to the first step, or alternatively, byphysically separating such a heavy fraction from the product of thesecond step and recycling it to the first and/or second step. For thetwo-stage hydrogen treatment involving such recycling, the inlet for theheavy feedstock oil does not always need to be provided before the firststep, but may be positioned between the first and second steps, orbetween the second step and the step for separating the light and heavyfractions. The step of separating the light and heavy fractions does notrequire any special method, but may be performed by distillation,solvent deasphalting, or any other ordinary method.

As already pointed out, the two-stage hydrotreating process of thisinvention accomplishes efficiently removal of metals from a heavy oil,decomposition of asphaltenes, and desulfurization, thereby producing aproduct oil having a high added value. The product oil, which containsreduced quantities of nitrogen and Conradson carbon residue, is anoptimum stock for prparing high grade gasoline by catalytic cracking, orkerosene, jet fuel oil and diesel oil by hydrocracking.

If the oil obtained by the two-stage process of this invention issubjected to catalytic cracking in a customary manner, it should notcontain any greater than 50 ppm, preferably 10 ppm, of nickel andvanadium, or any greater than 10% by weight, preferably 4% by weight, ofConradson carbon residue. If the oil is used for hydrocracking in aconventional manner, it should not contain any greater than 10 ppm,preferably 1 ppm, of nickel and vanadium by weight, or any greater than10% by weight, preferably 4% by weight, of Conradson carbon residue, orany greater than 2,000 ppm by weight, preferably 1,500 ppm by weight, ofnitrogen. The catalytic cracking of the oil can be carried out by usinga known apparatus, for example, a fluidized bed apparatus which iswidely used for preparing gasoline having a high octane value.Hydrocracking may be carried out by a fixed bed system to producekerosene, jet fuel oil, diesel oil, etc.

The following examples will further illustrate the present invention.

EXAMPLES OF CATALYST PREPARATION Example 1

Five liters of demineralized water was placed in a stainless steelcontainer provided with an external mantle heater, and heated to 95° C.1 Kg of aluminum nitrate, Al(NO)₃)₃.9H₂ O, was dissolved in water toform 2.5 liters of an aqueous solution thereof, and 500 cc of thisaqueous solution was added into the container. The solution in thecontainer was held at 95° C., and while it was being stirred, 14% byweight of aqueous ammonia was added to control the solution to pH 8. Thesolution was aged for one hour under boiling condition to form a seedalumina hydrosol. Then, 500 cc of the aforementioned aqueous aluminumnitrate solution was added into the hydrosol, and the hydrosol wasallowed to stand for 10 minutes. The hydrosol had a pH of 4. After itwas confirmed that the hydrosol had a temperature of at least 95° C.,14% by weight of aqueous ammonia was added into the hydrosol to controlit to pH 9, while it was being stirred, and the hydrosol was allowed tostand for 10 minutes. This pH control operation was repeated three moretimes i.e. a total of six pH adjustments. Then, the hydrosol was agedfor one hour under boiling condition to form an alumina hydrogel. Thewashing of this hydrogel was carried out by dispersing it in 20 litersof demineralized water and dehydrating it through a vacuum filter. Thiswashing operation was repeated three times, and the hydrogel wasdehydrated through the vacuum filter to yield a cake containing about25% by weight of alumina in terms of Al₂ O₃. This cake was formed intocylindrical particles having a diameter of 1 mm by an extruder providedwith a die having a hole with a diameter of 1.0 mm. The molded productwas heated at about 120° C. for two hours for drying, and precalcined at550° C. in an electric furnace for three hours.

Molybdenum and cobalt were supported on the precalcined product. Forthis purpose, 400 ml of warm water was added into 151.9 g of ammoniummolybdate. An aqueous solution obtained by dissolving 160.5 g of cobaltnitrate in 400 ml of distilled water was added into the ammoniummolybdate solution and mixed therewith, and 500 ml of aqueous ammoniahaving a concentration of 25% by weight was added into the mixture. 35ml of the solution obtained was diluted with 5 ml of distilled water,and the diluted solution was uniformly sprayed on 50 g of theprecalcined product, so that the precalcined product might beimpregnated with the solution. The precalcined product was kept in ahermetically sealed condition overnight, and air dried at roomtemperature. It was, then, dried with hot air at 120° C. for threehours, and calcined at 600° C. for three hours in an air stream, wherebyCatalyst I was prepared.

Example 2

The procedures of Example 1 were repeated, except that the pH controlwas repeated at intervals of 15 minutes, whereby Catalyst II containingcobalt and molybdenum was obtained.

Example 3

The procedures of Example 1 were repeated, except that the pH controlwas repeated for 10 times for holding the hydrosol on the acidic sidefor 5 minutes each time, while it was held for 30 minutes on thealkaline side, whereby Catayst III containing cobalt and molybdenum, andhaving an catalyst particle diameter of 1/32 inch was obtained.

Likewise, differently sized catalysts were prepared by using extrusionmolding dies having holes with diameters of 0.5 mm, 0.75 mm, 1.5 mm, 2mm and 4 mm, and had a catalyst outside particle diameter of 1/64 in.,1/48 in., 1/24 in., 1/16 in. and 1/8 in., respectively. A precalcinedproduct was prepared by the method by which Catalyst III was formed, andcatalyst metals were supported on the precalcined product as describedin Example 1, whereby Catalyst XV was obtained. This precalcined productwas also used to from Catalyst XVI carrying 2% by weight of molybdenumin terms of molybdenum oxide, Catalyst XVII carrying 6% by weightthereof, Catalyst XVIII carrying 10% by weight thereof, and Catalyst XIXcarrying 20% by weight thereof.

Example 4

Four liters of an aqueous solution of basic aluminum nitrate containing5% by weight of aluminum in terms of Al₂ O₃ (formed by dissolvingmetallic aluminum in nitric acid, NO₃ ⁻ /Al=0.48) was heated at 150° C.for three hours in a stainless steel autoclave, whereby a white seedalumina hydrosol was obtained. Two liters of the hydrosol solution wasdiluted with demineralized water to 10 liters, and the diluted solutionwas heated at 95° C. in a stainless steel container provided with anexternal mantle heater. Added thereinto was 250 cc of an aqueoussolution containing 400 g of aluminum nitrate, Al(NO₃)₃.9H₂ O, perliter, and the hydrosol was allowed to stand for five minutes. It had apH of 3. After it was ascertained that the hydrosol had a temperature ofat least 95° C., 14% by weight aqueous ammonia was added into thehydrosol to control it to pH 9, while it was being stirred, and thehydrosol was held for 10 minutes. The pH control was repeated two moretimes i.e. a total of four pH adjustments. Thereafter, the procedures ofExample 1 were repeated to yield Catalyst IV containing cobalt andmolybdenum.

Example 5

Fourteen liters of an aqueous solution of basic aluminum nitrate (NO₃ ⁻/Al=0.48) containing 1.6% by weight of aluminum in terms of Al₂ O₃ washydrothermally treated as described in Example 4, whereby a seed aluminahydrogel was prepared. 5.3 liters of the hydrogel was diluted to 10liters, and the diluted hydrogel was heated to 95° C. in a stainlesssteel vessel provided with an external mantle heater. Added thereintowas 50 cc of an aqueous solution containing 400 g of aluminum nitrate,Al(NO₃)₃.9H₂ O, per liter, and the hydrogel was held for five minutes.Its pH was 3. Then, while it was held at 95° C., 14% by weight aqueousammonia was added into the hydrogel to control it to pH 9, while it wasbeing stirred, and the hydrogel was held for 10 minutes. The pH controlwas repeated once more, and thereafter, the procedures of Example 1 wererepeated to yield Catalyst V containing cobalt and molybdenum.

Example 6

Fourteen liters of an aqueous solution of basic aluminum nitrate (NO₃ ⁻/Al=0.48) containing 1.4% by weight of aluminum in terms of Al₂ O₃ washeated at 150° C. for three hours in a stainless steel autoclave,whereby a white seed alumina hydrosol was prepared. 6.3 liters of thehydrosol solution was diluted with demineralized water to 10 liters, andthe diluted solution was heated to 95° C. in a stainless steel vesselprovided with an external mantle heater. Added thereinto was 160 cc ofan aqueous solution containing 400 g of aluminum nitrate, Al(NO₃)₃.9H₂O, per liter, and the hydrosol was held for one hour. Its pH was 3.Then, while the hydrosol was maintained at 95° C., 14% by weight aqueousammonia was added thereinto to control it to pH 9, while it was beingstirred, and the hydrosol was held for one minute. The pH control wasrepeated once more, and thereafter, the procedures of Example 1 wererepeated to yield Catalyst VI containing cobalt and molybdenum.

Example 7

An aluminum sulfate solution having a concentration of 76.6 g/liter interms of Al₂ O₃ was heated to, and held at 100° C. 18 liters ofdemineralized water was heated to 100° C. in a container capable ofbeing heated from outside. Added thereinto was 12 liters of the aqueousaluminum sulfate solution, and while they were strongly stirred, anaqueous solution containing 200 g/liter of sodium hydroxide was quicklyadded thereinto to control it to pH 11. The resulting solution was agedat 100° C. for one hour, while it was being stirred, whereby a seedalumina hydrosol was prepared. Then, 2 liters of aluminum sulfatesolution was added into the hydrosol to control it to pH 11, and thehydrosol was held for 55 minutes. The pH control was repeated four moretimes. The alumina hydrogel was filtered, and washed until no sulfuricacid radical was detected in the filtrate. The filter cake was carefullydispersed in 30 liters of demineralized water to form a sol. The sol washeated to 100° C., and its pH control was repeated three times, wherebyan alumina hydrogel was prepared. Then, it was washed by filtrationuntil no sulfuric acid radical was detected in the filtrate, whereby afilter cake was formed. Thereafter, the procedures of Example 1 wererepeated to yield Catalyst VII containing cobalt and molybdenum.

Example 8

An aqueous solution of aluminum nitrate having a concentration of 50g/liter in terms of Al₂ O₃ was heated to, and held at 100° C. 18 litersof demineralized water was heated to 100° C. in a vessel capable ofbeing heated from outside. Added thereinto was 12 liters of the aluminumnitrate solution, and while they were strongly stirred, aqueous ammoniahaving a concentration of 14% by weight was quickly added thereinto tocontrol it to pH 10. The resulting solution was aged at 100° C. for twohours, while it was being stirred, whereby a seed alumina hydrosol wasprepared. Then, 2 liters of aluminum nitrate solution was added into thehydrosol to control it to pH 4, and the hydrosol was held for 5 minutes.Aqueous ammonia having a concentration of 14% by weight was added intothe hydrosol to control it to pH 10, and it was held for 55 minutes. ThepH control was repeated for nine more times, and the hydrosol was agedat 100° C. for three hours, whereby an alumina hydrogel was obtained.The hydrogel was washed carefully to form a filter cake. Thereafter, theprocedures of Example 1 were repeated, except that the calcination wascarried out at 700° C. for three hours, to yield Catalyst VIIIcontaining cobalt and molybdenum.

Example 9

The procedures of Example 8 were repeated, except that the pH controlwas repeated seven times, and that the calcination was carried out at750° C. for three hours, whereby Catalyst IX was prepared.

Example 10

Fourteen liters of an aqueous solution of basic aluminum nitrate (NO₃ ⁻/Al=0.48) having a concentration of 4% by weight in terms of Al₂ O₃ washydrothermally treated at 140° C. for two hours in a stainless steelautoclave, whereby a white seed alumina hydrogel was prepared. Fiveliters of the hydrogel solution was diluted with demineralized water to10 liters, and the diluted solution was boiled in a stainless steelcontainer capable of being heated from outside. Added thereinto was oneliter of an aqueous solution containing 500 g/liter of aluminum nitrate,Al(NO₃)₃.9H₂ O, and the solution was held for five minutes. Then, whilethe hydrosol was maintained at 95° C., aqueous ammonia having aconcentration of 14% by weight was added thereinto to control it to pH10, and the hydrogel was held for five minutes. The pH control wasrepeated once more, and an alumina hydrogel was obtained. Thereafter,the procedures of Example 1 were repeated, except that the calcinationwas carried out at 650° C. for three hours, to yield Catalyst Xcontaining cobalt and molybdenum.

Example 11

An aqueous sulfuric acid solution was obtained by dissolving 154 g ofconcentrated sulfuric acid in 5,820 g of demineralized water. Asuspension of fine silica particles was prepared by adding 2,276 g ofwater glass (aqueous sodium silicate solution, JIS No. 3)instantaneously into the aqueous sulfuric acid solution, while it wasbeing strongly stirred. The suspension had a pH of about 5, andcontained 8.0% by weight of silica. The whole quantity of the silicasuspension was mixed with 8,250 g of an aqueous aluminum sulfatesolution containing 8.0% by weight of alumina, whereby a uniformaluminum sulfate-silica suspension (hereinafter referred to simply asthe "mixed solution") was obtained.

Then, 2,500 g of the mixed solution was added into 17,500 g ofdemineralized water in a 40 liter stainless steel vessel with a cover,and while the mixture was being stirred, it was heated to 100° C., andafter 370 g of 14% aqueous ammonia was added to precipitate the aluminumin the form of an hydroxide, the solution was contriolled to pH 8.0 to9.0, and held at 100° C. for 20 minutes, while it was being stirred,whereby a seed silica-alumina hydrosol was obtained. 1,000 g of themixed solution was added into the hydrosol to control it to pH 4, andafter stirring and heating were continued for 10 minutes, 160 g of 14 wt% aqueous ammonia was added into the hydrosol. The hydrogel in thevessel had a pH of 8 to 9, and stirring and heating were continued for20 minutes. The pH control was repeated thirteen times. The hydrogel inthe container was transferred into a vacuum filtration apparatus,whereby about 9,000 g of a white filter cake was obtained. The filtercake was dispersed in 30 liters of demineralized water at 80° C., andafter elution of sulfate from the precipitate, it was dehydrated andcleaned by the vacuum filtration apparatus. The cleaning operation wasrepeated five times, whereby 7,200 g of a white filter cake having asolids content of 18.2% by weight was obtained. This cake was extrusionmolded by a piston type extruder having a die formed with 50 holes eachhaving a diameter of 1.2 mm. The molded products were dried in a hot airdrier, and after evaporation of almost all the water therefrom, theywere further dried at 120° C. for one hour. Then, they were precalcinedat 550° C. for three hours in an electric furnace, whereby there wereultimately obtained 1,310 g of calcined cylindrical silica-aluminaparticles each having a diameter of 0.8 mm.

This silica-alumina carrier was found to contain 49% of SiO₂, 49% of Al₂O₃, 0.5% of H₂ O, 0.4% of SO₄ and 0.01% of Na₂ O.

Thereafter, the procedures of Example 1 were repeated to yield CatalystXI containing cobalt and molybdenum.

Example 12

20 kg of water was placed in a 40 liter capacity stainless steel vesselwith a cover, and 500 g of water glass (JIS No. 3) was added thereinto.After the solution was heated to 95° C., there was added 290 g of anaqueous aluminum sulfate solution containing 8.0% by weight of alumina.This procedure lowered the pH of the solution to 8.0, and there wasformed a white precipitate composed of hydroxides of aluminum andsilicon. After stirring was continued for 15 minutes, there was formed aseed silica-alumina hydrosol. 500 g of water glass (JIS No. 3) was addedinto the hydrosol to control its pH to about 11.5. While stirring wasfurther continued for five minutes, 290 g of aqueous aluminum sulfatesolution containing 8.0% by weight of alumina was added into thehydrosol, and it was held for 15 minutes. Such alternate addition ofwater glass and an aqueous solution of aluminum sulfate was repeatedfive times at regular intervals, whereby a white slurry was formed inthe vessel. The slurry was transferred into a vacuum filtrationapparatus and cleaned carefully, whereby there was ultimately obtained4,670 g of a filtered cake having a solids content of 18% by weight.Thereafter, the procedures of Example 11 were repeated to yield 840 g ofa silica-alumina carrier composed of 0.8 mm dia. cylindrical particles.The carrier was found to contain 85.5% of SiO₂, 13.3% of Al₂ O₃, 0.05%of Na₂ O, 0.5% of H₂ O and 0.5% of SO₄.

Example 13

One liter of an aqueous magnesium chloride solution containing 260 g ofmagnesium chloride, MgCl₂.6H₂ O, per liter was added into 5 liters ofwater, and the mixed solution was maintained at room temperature. Oneliter of an aqueous solution containing 344 g of sodium silicate (JISNo. 3) per liter was added into the aqueous magnesium chloride solution,while it was being stirred, followed by gradual addition of a solutioncontaining 200 g/liter of sodium hydroxide, NaOH, to control the mixedsolution to pH 9. The solution was aged at 50° C. for 20 hours, wherebya seed silica hydrosol was obtained. 0.5 liter of the magnesium chloridesolution was added into the hydrosol, and it was held for 10 minutes.Then, 0.5 liter of the sodium silicate solution and further the sodiumhydroxide solution were added into the hydrosol to control it to pH 9,and the hydrosol was held for 10 minutes. The pH control was repeatedfour more times. Then, the sodium hydroxide solution was added into thehydrosol to control its pH to 10, and after it was aged at about 50° C.for five hours, there was obtained a silica-magnesia hydrogel.Thereafter, the procedures of Example 1 were repeated to yield CatalystXIII containing cobalt and molybdenum.

Example 14

An aqueous solution containing 428 g/liter of titanium tetrachloride,TiCl₄, was prepared by dissolving titanium tetrachloride gradually indistilled water, while it was cooled. There was also prepared an aqueoussolution containing 620 g/liter of aluminum nitrate, Al(NO₃)₂.9H₂ O.Five liters of demineralized water was heated to 95° C. in a glasscontainer provided with an external mantle heater. Added thereinto were1 liter of the aluminum nitrate solution and 200 cc of the titaniumtetrachloride solution. While the mixed solution was maintained at 95°C., 14 wt % aqueous ammonia was added to control it to pH 9. Then, thesolution was aged for two hours under boiling condition, whereby seedalumina-titania hydrogel was obtained. 500 cc of the aluminum nitratesolution and 100 cc of the titanium tetrachloride solution were addedinto the hydrogel, and it was held for five minutes, while beingstirred. Then, 14 wt % aqueous ammonia was added into the hydrogel tocontrol it to pH 9. The pH control was repeated seven more times, andthereafter, the hydrosol was aged for three hours under boilingcondition, whereby an alumina-titania hydrogel was obtained. Thereafter,the procedures of Example 1 were repeated to yield Catalyst XIVcontaining cobalt and molybdenum.

Comparative Example (Preparation of Sepiolite Catalyst)

Clay-like Spanish sepiolite was dried with hot air at about 120° C. forsix hours, and ground in a ball mill for about six hours, whereby therewas formed sepiolite powder having a particle size not greater thanabout 50 mesh, and of which at least 90% of particles had a particlesize not greater than 100 mesh.

An aqueous solution of aluminum sulfate having a concentration of 76.6g/liter in terms of Al₂ O₃ was heated to, and held at 100° C. Eighteenliters of demineralized water was heated to 100° C. in a vessel capableof being heated from outside. Twelve liters of the aluminum sulfatesolution was added into the demineralized water, and while it was beingstrongly stirred, 4.4 liters of 28% aqueous ammonia was added into thesolution quickly to control it to pH 9. Then, the solution was aged at100° C. for one hour while being stirred, whereby a seed aluminahydrosol was obtained. Two liters of the aluminum sulfate solution wasadded into the hydrosol, and after it was held for one hour, 28 wt %aqueous ammonia was added into the hydrosol to control it to pH 9, andit was held for one minute. The pH control was repeated nine times.Then, the hydrosol was cleaned until no sulfuric acid radical wasdetected in the filtrate, whereby there was formed a filter cake havinga concentration of about 20% by weight in terms of Al₂ O₃.

Then, 5 kg of sepiolite powder, 7 kg of the cake (as molding assistance)and 2 kg of water were mixed together, and kneaded carefully in akneading machine. The kneaded mixture was extrusion molded by anextruder having a die provided with 0.9 mm dia. holes. The moldedproduct was dried at about 120° C. for two hours, and calcined at 500°C. for three hours in an electric oven. Thereafter, the procedures ofExample 1 of this invention were repeated to yield Catalyst XXIIIcontaining cobalt and molybdenum.

Example 15

Catalyst XX was impregnated with a warm aqueous solution containingabout 4 wt % of orthoboric acid to the extent that the catalystcontained 6.5% by weight of boria. The catalyst was dried with hot airat 120° C. for three hours, and calcined at 500° C. for two hours toyield Catalyst XXIV.

The properties of the catalysts prepared as set forth above are shown inTable 3-1. Catalyst XV comprises a carrier having no catalytic metalcomponent supported thereon. "Limit pore volume" referred to in Tables3-1 and 3-2 shows a value calculated according to the followingequation:

    Limit pore volume (cc/g)=0.46/[1-(100/APD).sup.2 ]

Example 16

A cake having a concentration of about 25% by weight in terms of Al₂ O₃was obtained as described in connection with Comparative Example 1.Thereafter, the procedures of Example 1 were repeated to yield CatalystNo. 1 shown in Table 6 which will appear later on.

Example 17

A cake having a concentration of about 20% by weight in terms of Al₂ O₃was prepared as described in connection with Example 4. This cake wasextrusion molded by an extruder having a die provided with 1.0 mm dia.holes. The molded product was quickly dried at about 300° C., andcalcined at 550° C. for three hours in an electric oven. Thereafter, theprocedures of Example 1 were repeated to yield Catalyst No. 4 shown inTable 6.

Example 18

A cake having a concentration of about 20% by weight in terms of Al₂ O₃was prepared as described in Comparative Example 1, and thereafter, theprocedures of Example 17 were repeated to yield Catalyst No. 6 shown inTable 6.

                                      TABLE 3-1                                   __________________________________________________________________________    Properties of Catalyst                                                        NO.       I  II III                                                                              IV V  VI VII                                                                              VIII                                                                             IX X  XV XVI                                                                              XVII                                                                             XVIII                                                                            XIX                       __________________________________________________________________________    Composition                                                                   (wt %)                                                                        CoO       2.0                                                                              2.0                                                                              1.9                                                                              1.9                                                                              1.9                                                                              2.2                                                                              2.1                                                                              1.9                                                                              2.0                                                                              1.9                                                                              0.0                                                                              0.0                                                                              0.0                                                                              0.0                                                                              0.0                       MoO.sub.3 5.7                                                                              5.4                                                                              5.3                                                                              5.0                                                                              5.4                                                                              5.7                                                                              5.4                                                                              5.6                                                                              5.4                                                                              5.4                                                                              0.0                                                                              1.9                                                                              6.1                                                                              9.8                                                                              20.3                      Al.sub.2 O.sub.3                                                                        90.9                                                                             91.4                                                                             91.8                                                                             92.2                                                                             92.0                                                                             89.9                                                                             91.0                                                                             91.4                                                                             90.6                                                                             91.1                                                                             98.0                                                                             9.59                                                                             91.3                                                                             87.2                                                                             77.2                      Average   1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                       catalyst diameter                                                             (mm)                                                                          Pore volume (cc/g)                                                             75-100 Å                                                                           0.05                                                                             0.01                                                                             0.01                                                                             0.03                                                                             0.03                                                                             0.02                                                                             0.02                                                                             0.01                                                                             0.02                                                                             0.01                                                                             0.02                                                                             0.02                                                                             0.01                                                                             0.01                                                                             0.01                      100-180 Å                                                                           0.50                                                                             0.45                                                                             0.11                                                                             0.06                                                                             0.05                                                                             0.03                                                                             0.12                                                                             0.07                                                                             0.11                                                                             0.07                                                                             0.14                                                                             0.13                                                                             0.10                                                                             0.13                                                                             0.13                      180-400 Å                                                                           0.02                                                                             0.35                                                                             0.81                                                                             0.73                                                                             0.16                                                                             0.07                                                                             0.95                                                                             0.56                                                                             0.37                                                                             0.38                                                                             0.80                                                                             0.82                                                                             0.86                                                                             0.79                                                                             0.67                      400-500 Å                                                                           0.00                                                                             0.01                                                                             0.01                                                                             0.14                                                                             0.12                                                                             0.03                                                                             0.01                                                                             0.01                                                                             0.02                                                                             0.01                                                                             0.02                                                                             0.02                                                                             0.01                                                                             0.01                                                                             0.01                      500-1500 Å                                                                          0.00                                                                             0.00                                                                             0.03                                                                             0.05                                                                             0.65                                                                             0.82                                                                             0.03                                                                             0.03                                                                             0.05                                                                             0.01                                                                             0.08                                                                             0.04                                                                             0.02                                                                             0.02                                                                             0.02                      >1500 Å                                                                             0.01                                                                             0.03                                                                             0.02                                                                             0.03                                                                             0.02                                                                             0.05                                                                             0.02                                                                             0.02                                                                             0.03                                                                             0.03                                                                             0.03                                                                             0.03                                                                             0.02                                                                             0.01                                                                             0.01                      Total     0.58                                                                             0.85                                                                             0.99                                                                             1.04                                                                             1.03                                                                             1.03                                                                             1.15                                                                             0.70                                                                             0.60                                                                             0.51                                                                             1.09                                                                             1.06                                                                             1.02                                                                             0.97                                                                             0.85                      Specific surface                                                                        186                                                                              221                                                                              165                                                                              139                                                                              104                                                                              65 191                                                                              119                                                                              104                                                                              83 174                                                                              177                                                                              169                                                                              163                                                                              155                       area (m.sup.2 /g)                                                             Average pore                                                                            125                                                                              163                                                                              240                                                                              298                                                                              396                                                                              631                                                                              241                                                                              235                                                                              232                                                                              246                                                                              251                                                                              240                                                                              242                                                                              238                                                                              220                       diameter (Å)                                                              Limit pore volume                                                                       1.28                                                                             0.74                                                                             0.56                                                                             0.52                                                                             0.49                                                                             0.47                                                                             0.56                                                                             0.56                                                                             0.56                                                                             0.55                                                                             0.55                                                                             0.56                                                                             0.55                                                                             0.56                                                                             0.58                      (cc/g)                                                                        Catalyst density                                                                        0.60                                                                             0.47                                                                             0.45                                                                             0.44                                                                             0.45                                                                             0.41                                                                             0.40                                                                             0.58                                                                             0.64                                                                             0.71                                                                             0.42                                                                             0.44                                                                             0.44                                                                             0.47                                                                             0.54                      (g/cc)                                                                        Crushing strength                                                                       5.3                                                                              3.2                                                                              2.6                                                                              2.1                                                                              1.9                                                                              1.3                                                                              2.2                                                                              3.3                                                                              3.5                                                                              4.1                                                                              2.0                                                                              2.1                                                                              2.4                                                                              2.7                                                                              3.3                       (kg)                                                                          __________________________________________________________________________

                                      TABLE 3-2                                   __________________________________________________________________________    Properties of Catalyst                                                        NO.       XI  XII XIII                                                                              XIV XX  XXI XXII                                                                              XXIII                                                                             XXIV                                __________________________________________________________________________    Composition                                                                   (wt %)                                                                        CoO       2.0 2.0 2.0 2.0 1.2 4.1 3.5 2.0 1.1                                 MoO.sub.3 6.0 6.0 6.0 6.0 11.0                                                                              15.0                                                                              15.0                                                                              5.8 6.5                                 Al.sub.2 O.sub.3                                                                        45.1                                                                              10.3                                                                              --  64.4                                                                              86.8                                                                              78.4                                                                              81.0                                                                              5.8 81.2                                SiO.sub.2 45.1                                                                              81.4                                                                              48.0                                                                              --  --  --  --  52.6                                                                              --                                  TiO.sub.2 --  --  --  27.6                                                                              --  --  --  --  --                                  MgO       --  --  45.0                                                                              --  --  --  --  20.9                                                                              --                                  NiO       --  --  --  --  0.8 --  --  --  0.7                                 B.sub.2 O.sub.3                                                                         --  --  --  --  --  --  --  --  6.5                                 Average   1.0 1.0 1.0 1.0 1.0 1.1 1.0 1.2 1.0                                 catalyst diameter                                                             (mm)                                                                          Pore volume (cc/g)                                                             75-100 Å                                                                           0.06                                                                              0.05                                                                              0.10                                                                              0.04                                                                              0.05                                                                              0.01                                                                              0.10                                                                              0.03                                                                              0.02                                100-180 Å                                                                           0.30                                                                              0.15                                                                              0.20                                                                              0.15                                                                              0.47                                                                              0.48                                                                              0.10                                                                              0.08                                                                              0.48                                180-400 Å                                                                           0.60                                                                              0.63                                                                              0.40                                                                              0.28                                                                              0.02                                                                              0.07                                                                              0.04                                                                              0.14                                                                              0.02                                400-500 Å                                                                           0.00                                                                              0.03                                                                              0.00                                                                              0.04                                                                              0.00                                                                              0.00                                                                              0.01                                                                              0.05                                                                              0.00                                500-1500 Å                                                                          0.06                                                                              0.12                                                                              0.03                                                                              0.08                                                                              0.00                                                                              0.01                                                                              0.05                                                                              0.39                                                                              0.00                                >1500 Å                                                                             0.02                                                                              0.03                                                                              0.02                                                                              0.02                                                                              0.00                                                                              0.01                                                                              0.21                                                                              0.03                                                                              0.00                                Total     1.04                                                                              1.01                                                                              0.75                                                                              0.61                                                                              0.54                                                                              0.58                                                                              0.51                                                                              0.72                                                                              0.52                                Specific surface                                                                        189 129 155 97  190 153 93  86  191                                 area (m.sup.2 /g)                                                             Average pore                                                                            220 312 194 251 115 149 219 336 111                                 diameter (Å)                                                              Limit pore volume                                                                       0.58                                                                              0.51                                                                              0.63                                                                              0.55                                                                              1.89                                                                              0.84                                                                              0.58                                                                              0.50                                                                              --                                  (cc/g)                                                                        Catalyst density                                                                        0.43                                                                              0.44                                                                              0.50                                                                              0.65                                                                              0.69                                                                              0.66                                                                              0.53                                                                              0.56                                                                              0.74                                (g/cc)                                                                        Crushing strength                                                                       2.6 2.3 3.0 3.8 5.4 4.8 4.6 2.5 6.4                                 (kg)                                                                          __________________________________________________________________________

Example 19

The procedures of Example 10 were repeated, except that the hydrothermaltreatment of basic aluminum nitrate was carried out at 150° C. for twohours, whereby Catalyst No. 7 was prepared as shown in Table 6.

Example 20

The procedures of Example 19 were repeated, except that the pH controlwas repeated three times, whereby Catalyst No. 8 was obtained as shownin Table 6.

Attention is now directed to examples concerning the hydrotreatment ofthe feedstock oils, of which the properties have hereinbefore beenshown. The apparatus, and the methods for analyzing the feedstock oiland the oil obtained by the treatment were as follows:

Hydrogen Treating Apparatus

A fixed bed flow type reactor having its pressure, temperature and flowrate controlled automatically was used for the hydrotreatment which willbe described in the following examples. The reactor included a stainlesssteel reaction vessel having an inside diameter of 25 mm and a length of1,000 mm, and provided centrally therethrough with a downwardly directedthermowell having an outside diameter of 8 mm. The temperature of thereaction vessel was controlled by six electrically heated aluminumblocks. The stock oil was measured by an integrated flow meter, and fedquantitatively into the reaction vessel by a two-throw reciprocatingpump. Hydrogen was supplied into the reaction vessel after its flow ratewas measured through a high pressure flow meter. The gas and the liquidin the reaction vessel were co-current downwardly. The reaction vesselcontained 200 cc of catalyst, and the spaces above and below thecatalyst bed were each filled with about 30 cc of inert alumina beads.The effluent from the reaction zone was introduced into a gas-liquidseparator, and the liquid separated from the gas was collected into aliquid product receptacle through a pressure control valve, while thegas was caused to flow through a pressure control valve, measured by awet flow meter, analyzed by process gas chromatography and dischargedfrom the system. The same equipment as hereinabove set forth was usedfor the two-stage hydrotreatment, except that a pair of reaction vesselswere connected in series with each other.

Analysis of Feedstock and Product Oils

The general analysis of the properties was carried out by usingcustomary methods for petroleum analysis. Asphaltene was determined inaccordance with the method for analyzing the n-heptane insolubles basedon U.O.P. Method No. 614-68. The average molecular weight was determinedby vapor pressure osmosis in a pyridine solution at 60° C., using aHitachi Corona 111 apparatus. The molecular weight distribution wasdetermined by gel permeation chromatography, using a Model LC-08apparatus made by Nippon Bunseki Kogyo, Japan. A total of four SHODEXgels made by Showa Denko and each in a column having an inside diameterof 20 mm and a length of 600 mm were connected in series with eachother. They were one SHODEX A-802, two SHODEX A-803 and one SHODEXA-804. Chloroform was used as a solvent at 30° C., and detection wasmade by a differential refractometer.

Catalyst Performance Test 1

Experiments were conducted for the hydrotreatment of Boscan crude oil A,of which the properties have been shown in Table 1, at a reactiontemperature of 405° C., a hydrogen pressure of 140 atm., a LHSV of 1.0hour⁻¹ and an oil to hydrogen ratio (Normal liter/liter) of 1,000 inorder to compare the performance of commercially available Catalysts XX,XXI and XXII used for hydrodesulfurization or hydrodemetallization ofheavy hydrocarbon oils, sepiolite Catalyst XXIII for hydrotreatment, andCatalyst III of this invention. The results of the experiments are shownin FIG. 2.

FIG. 2 is a graph showing the relation, changing with the lapse of time,between the decomposition rate of asphaltenes (wt %) and the quantity ofmetal deposited by the feedstock oil on the catalyst (wt % according tothe new catalyst standard). The quantity of metal deposition indicates atotal of vanadium and nickel, as will be the case hereinafter, too. InFIG. 2, curve 1 represents the results obtained with Catalyst III ofthis invention, curve 2 shows the results of the tests conducted withsepiolite catalyst XXIII, and curves 3, 4 and 5 shows the resultsobtained with known catalysts XXII, XXI and XX.

As is obvious from the results shown in FIG. 2, the catalyst of thisinvention defines a remarkable improvement in its activity fordecomposition of asphaltenes, and its stability or life over any knowncatalyst. It will be noted that the catalyst of this invention defines aremarkable improvement over any sepiolite catalyst. Even if about 80% byweight of metal is deposited on the catalyst surface, the catalyst ofthis invention does not undergo any appreciable reduction in itsactivity for asphaltene decomposition. Catalysts having such activityand stability have heretofore not been known in the art, but have beendeveloped for the first time by the inventors of this invention.

The oil obtained by the foregoing experiments was analyzed, andexamination was made of the average molecular weight of the asphalteneremaining therein, and the variation with the lapse of time in the rateof sulfur and metal removal from asphaltenes. These are shown in FIG. 3in relation to the quantity of the metal deposited on the catalyst. InFIG. 3, curves 6, 7 and 8 represent the results of the experiments inwhich the catalyst of this invention was used, and indicate the rate ofdesulfurization, the rate of metal removal and the average molecularweight of the residual asphaltenes, respectively, in relation to thequantity of the metal deposited on the catalyst. Likewise, curves 9, 10and 11 represent the results obtained by using known, commerciallyavailable Catalyst XXI, and show the rate of desulfurization, the rateof metal removal and the average molecular weight of the residualasphaltenes, respectively, in relation to the quantity of the metaldeposited on the catalyst.

It is clearly understood from the results shown in FIG. 3 that thecatalyst of this invention can effectively reduce the molecular weightof asphaltenes, and can also efficiently remove sulfur and metal fromasphaltenes, as opposed to the known, commercially available catalyst.

FIG. 4 shows the relation between the decomposition rate of asphaltenesand the hydrogen consumption. In FIG. 4, curve 12 shows the resultsobtained by using the catalyst III of this invention, while curve 13represents those obtained by using known, commercially availableCatalyst XXI. It is obvious from the results shown in FIG. 4 that thecatalyst of this invention requires extremely less hydrogen for a givenrate of asphaltene decomposition than the known catalyst, and has a highdegree of selectivity for the hydrotreatment of asphaltenes.

It is noted from the foregoing experimental results that the catalyst ofthis invention is a very useful catalyst for the hydrotreatment of aheavy hydrocarbon oil containing a large quantity of asphaltenes,particularly for the pretreatment for producing a high grade light oil.

Catalyst Performance Test 2

Commercially available Catalysts XX and XXI, and the Catalyst VII ofthis invention were tested for hydrotreating deasphalted oil obtained bydeasphalting Boscan crude oil with n-pentane as a solvent at a pressureof 40 kg/cm² G, a temperature of 195° C. and a solvent ratio by volumeof 7. The deasphalted oil had a specific gravity of 17.1° API, andcontained 83.10% by weight of carbon, 11.32% by weight of hydrogen,46.1% by weight of sulfur, 0.33% by weight of nitrogen, a Conradsoncarbon residue of 7.96% by weight, 0.10% by weight of asphaltene, 35 ppmby weight of nickel and 306 ppm by weight of vanadium. The conditionsfor the hydrotreatment included a reaction temperature of 350° C., ahydrogen pressure of 140 atm., a LHSV of 2.0 hours⁻¹ and an oil tohydrogen ratio (Normal liter/liter) of 1,000. Table 4 shows the typicalproperties of the oils obtained after the lapse of about 50 hours, andthe conversion ratio for each reaction are shown in Table 4. Boscancrude oil A was also hydrotreated in the same way, and the results shownin Table 4 were obtained.

It is noted from these experimental results that while the knowncatalysts are more active for the removal of sulfur and vanadium fromthe feedstock oil not containing asphaltene than the catalyst of thisinvention, the catalyst of this invention has a higher activity forvanadium removal and asphaltene decomposition if the feedstock oilcontains asphaltenes. It is also noted that the catalyst of thisinvention is suitable for the first step for the two-stagehydrotreatment of a heavy hydrocarbon oil containing large quantities ofasphaltenes and heavy metals, by using a known highly active catalyst.

                                      TABLE 4                                     __________________________________________________________________________    Properties of oils hydrotreated by                                            various types of catalysts, and rate of each                                  reaction involved.                                                                         Desul-   Vana-     Asphal-                                                    furiza-                                                                            Vana-                                                                             dium Asphal-                                                                            tene                                                   Sulfur                                                                            tion dium                                                                              removal                                                                            tene decomposi-                                    Stock                                                                             Cata-                                                                              content                                                                           rate content                                                                           rate content                                                                            tion rate                                     oil lyst (wt %)                                                                            (wt %)                                                                             (ppm)                                                                             (wt %)                                                                             (wt %)                                                                             (wt %)                                        __________________________________________________________________________    DA* XX   1.61                                                                              65    48 84   --   --                                            DA  XXI  3.51                                                                              24    92 70   --   --                                            DA  VII  3.81                                                                              17   140 54   --   --                                            A   XX   0.76                                                                              86   372 70   4.1  65                                            A   XXI  0.86                                                                              84   310 75   4.1  65                                            A   VII  2.47                                                                              54   149 88   2.4  80                                            __________________________________________________________________________     *Deasphalted oil as hereinbefore referred to.                            

EXAMPLES OF HYDROTREATMENT Example 2-1

It has already been mentioned that the average pore diameter, APD, of acatalyst has a significant bearing on the activity for decomposition ofasphaltenes. Many experiments were conducted to verify the fact, and thefollowing is a description of Example 2-1.

Boscan crude oil A and Khafji vacuum residue C, of which the propertieshave been shown in Table 1, were hydrotreated by using Catalysts I, II,III, IV, V and VI having the properties shown in Table 3. The tests wereconducted under the same conditions as those set forth for CatalystPerformance Test 1 before. Due to the different concentrations ofasphaltene in the feedstock oils tested, the activity for asphaltenedecomposition was expressed by the secondary reaction rate constant, Ka,according to the following formula, rather than by the rate ofasphaltene decomposition:

    Ka=(1/A.sub.P -1/A.sub.F)·LHSV

in which A_(P) represents the weight in kg of asphaltenes remaining in 1kg of the oil obtained after 50 hours of operation, A_(F) represents theweight in kg of asphaltenes present in 1 kg of the feedstock oil, andLHSV represents the liquid space velocity expressed by the volumes ofthe feedstock oil fed for one volume of catalyst per hour.

The test results are graphically shown in FIG. 5, in which curve 14refers to Boscan crude oil A, and curve 15 to Khafji vacuum residue C.Symbols I, II, III, IV, V and VI refer to the catalysts tested.

It will be understood that the average pore diameter of about 180 Å toabout 400 Å provides a satisfactory activity for asphaltenedecomposition, and that the range of the average pore diameter which issuitable for asphaltene decomposition hardly differs with the oil to betreated. If the average pore diameter is less than about 180 Å, thediffusion of asphaltene molecules into the pores of the catalyst isseriously inhibited, while a catalyst having an average pore diametergreater than about 500 Å has a reduced surface area which is effectivefor the reaction, and has its activity lowered sharply by deposition ofcarbon on its surface. Catalysts III, IV and V fall within the scope ofthis invention, and have a superior degree of activity for asphaltenedecomposition as noted.

Example 2-2

This set of tests were conducted to examine the stability of theactivity of the catalysts. The tests were conducted by treating Boscancrude oil A with Catalysts I to VI under the same conditions as those ofExample 2-1 above. The results are shown in FIG. 6, in which curves 16to 21 refer to Catalysts III, IV, V, VI, II and I, respectively. Table 5shows the quantity of carbon deposited on the catalyst during each test.This quantity of carbon was determined by washing the catalyst withtoluene carefully, drying it at about 80° C. under reduced pressure,picking up a certain amount of a sample, burning it in an oxygen streamat 1,600° C. and measuring the amount of carbon dioxide formed. Thismethod is based on U.O.P. method No. 703-71. This determination wascarried out by using a 70 second carbon determinator manufactured byLaboratory Equipment Corporation, U.S.A.

                  TABLE 5                                                         ______________________________________                                        Quantity of Carbon deposited                                                  Catalyst    I      II      III  IV    V    VI                                 ______________________________________                                        Dwell time (h)                                                                            340    380     450  840   940  500                                Quantity of  6      8       12   15    18   40                                carbon deposited                                                              (wt % on new                                                                  catalyst)                                                                     ______________________________________                                    

As is obvious from the results of these tests, Catalysts III, IV and Vof this invention have a higher activity for asphaltene decompositionthan the other catalysts, and a higher degree of stability as they canmaintain its activity until after they have had about 80% by weight ofmetal deposited thereon. Catalyst VI is not only inferior in mechanicalstrength (crushing strength), but also fails to show satisfactoryactivity and stability with a large quantity of carbon deposited thereonas is apparent from the analysis of the catalyst used. Although thiscatalyst has a pore volume which is greater than the limited pore volumedefined by the following formula ##EQU8## its average pore diameter,surface area, and total volume of the pores having a diameter of 180 to500 Å fail to fall within the ranges defined by this invention. CatalystI has an average pore diameter and a limited pore volume which are bothbelow the ranges specified by this invention, while Catalyst II, whichhas a pore volume greater than its limited pore volume, has an averagepore diameter which is less than the range specified for this invention.Both of these catalysts show a sharp reduction in activity. Depositionof metal in the pores of the catalyst leads to sharp reduction in theeffective diameter, thereby seriously inhibiting the diffusion ofasphaltene molecules into the pores. By comparing the test results forCatalysts III, IV and V, it has been found that a catalyst has a highactivity for asphaltene decomposition, if its pore volume defined bypores having a diameter of 180 to 400 Å occupies a greater proportionrelative to the total pore volume of the pores having a diameter of 180to 500 Å.

Example 2 -3

The hydrotreatment of Boscan crude oil A was carried out by usingCatalysts III, VII, VIII, IX and X shown in Table 3-1 in order toexamine the relation between the stability of the activity of thecatalyst and its pores. The conditions for the treatment were equal tothose of Example 2-2. The test results are shown in FIG. 7, in whichcurves 22 to 26 refer to Catalysts III, VII, VIII, IX and X,respectively. Catalyst X has a pore volume which is smaller than itslimit pore volume. Its average pore diameter, surface area, and totalvolume of the pores having a diameter of 180 to 500 Å all fall withinthe ranges specified by this invention. However, as it hardly shows asatisfactory activity when it has had about 50% by weight of metaldeposited thereon, this catalyst is not suitable for the hydrotreatmentof a heavy hydrocarbon oil containing asphaltenes. Catalysts VIII, IIIand VII have higher activity and stability in the order mentioned.Catalysts having a pore volume which is greater than the limit porevolume as specified according to this invention are more efficientlyused per unit volume which they fill in a reactor, and suitable for thehydrotreatment of heavy hydrocarbon oils.

Example 2-4

The hydrotreatment of Boscan crude oil A was carried out under the sameconditions as those set forth in Example 3 above by using Catalysts IIIprepared in Example 2-3 of Catalyst Preparation and having averagecatalyst diameters, ACD, of 0.52 mm, 0.69 mm, 1.0 mm, 1.4 mm, 2.1 mm and4.1 mm, respectively, in order to examine the relation between theparticle diameter and its activity. After about 50 hours of operation,the concentration, of asphaltene in each oil produced was examined, andattempts were made to determine its relation to the reaction rateconstant Ka, i.e., ACD/(APD/100)⁰.5 as shown in Example 2-1. Thisrelation is shown in FIG. 8. It is noted from FIG. 8 that the activityof the catalyst is sharply reduced, if the value of ACD/(APD/100)⁰.5exceeds about 1.0. Therefore, it is important to ensure that the averagecatalyst diameter, ACD, of the catalyst be less than the value of(APD/100)⁰.5.

Catalyst Performance Test 3

Various catalysts having an alumina carrier were tested for crushingstrength. The results are shown in Table 6. It is noted from Table 6that no catalyst shows an industrially satisfactory strength greaterthan about 1.5 kg, if the volume of the pores having a diameter of atleast 1,500 Å exceeds about 0.03 cc/g. In other words, the crushingstrength of the catalyst is sharply reduced, with an increase in thevolume of the pores having a diameter of at least 1,500 Å.

In Table 6, Catalysts No. 2, No. 3, No. 5 and No. 9 correspond toCatalysts III, IV, V and VI, respectively, and Catalysts No. 1, No. 4,No. 6, No. 7 and No. 8 refer to Examples Nos. 16, 17, 18, 19 and 20,respectively.

                  TABLE 6                                                         ______________________________________                                        Crushing Strength of Catalyst                                                                PV              Pore   Crushing                                No.  ACD (mm)  (cc/g)  APD (Å)                                                                           Volume*                                                                              Strength (kg)                           ______________________________________                                        1    1.0       1.00    231     0.06   1.4                                     2    1.0       0.99    240     0.02   2.6                                     3    1.0       1.04    298     0.03   2.1                                     4    1.0       1.04    318     0.08   1.0                                     5    1.0       1.03    396     0.02   1.9                                     6    1.0       1.08    421     0.09   0.9                                     7    1.0       1.05    462     0.02   1.8                                     8    1.0       1.14    540     0.06   1.2                                     9    1.0       1.03    631     0.05   1.3                                     ______________________________________                                         *Volume (cc/g) of pores having a dia. of at least 1,500 Å.           

Catalyst Performance Test 4

Many catalysts having a pore volume less than 0.05 cc/g for pores havinga diameter of at least 1,500 Å were tested for crushing strength (SCS),and attempts were made to determine its relation to the average porediameter, APD, average catalyst diameter ACD and total pore volume PV.As the result, the following relation was established:

    SCS=762×ACD×APD.sup.-0.5 xe.sup.-3.95×PV /(PV+0.3)

FIG. 9 compares the values of strength calculated from this formula, andthose which are actually measured. In FIG. 9, each dot on the curveindicates the coincidence of the theoretical and actual values.

Therefore, it is noted that in order to obtain an industrially necessarystrength of at least 1.5 kg, a catalyst should have a total pore volumenot greater than the value calculated by the following formula: ##EQU9##

Example 2-5

Boscan crude oil A and Khafji vacuum residue were hydrotreated at areaction temperature of 405° C., a hydrogen pressure of 140 atm., a LHSVof 0.5 hour⁻¹, and a hydrogen to oil ratio (N liter/liter) of 1,000, byusing Catalysts III, XI, XII, XIII and XIV having different carriers.Table 7 shows the properties of the oils produced after 50 hours ofoperation. It is obvious from the results shown in Table 7 that anyporous carrier composed of at least one selected from among the elementsbelonging to Groups II, III and IV of the Periodic Table is effective asa carrier for the catalyst of this invention.

                  TABLE 7                                                         ______________________________________                                        Properties of oils hydrotreated                                               by various types of carriers                                                             Carrier                                                            Properties   III     XI     XII    XIII XIV                                   ______________________________________                                        Feedstock oil A                                                               Asphaltenes wt %                                                                           1.6     1.7    1.8    2.0  2.1                                   Conradson carbon                                                                           7.8     6.0    8.1    6.3  6.8                                   residue wt %                                                                  Sulfur wt %  1.6     1.2    1.5    1.4  1.5                                   Metal ppm                                                                     Ni           8       10     9      11   12                                    V            40      51     50     58   79                                    Feedstock oil C                                                               Asphaltenes wt %                                                                           1.8     2.0    1.9    2.3  2.6                                   Conradson carbon                                                                           9.2     9.0    10.5   9.6  9.7                                   residue wt %                                                                  Sulfur wt %  2.0     1.9    2.3    2.0  1.9                                   Metal ppm                                                                     Ni           13      13     14     14   15                                    V            14      16     18     20   25                                    ______________________________________                                    

Example 2-6

This example was intended for examining the relation between theactivity of a catalyst containing only molybdenum as the catalytic metalcomponent, and the amount of the molybdenum supported on an aluminacarrier. For this purpose, Boscan crude oil A was hydrotreated at atemperature of 405° C., a hydrogen pressure of 140 atm., a LHSV of 1.0hour⁻¹ and a hydrogen to oil ratio (N liter/liter) of 1,000 by usingCatalyst XV, XVI, XVII, XVIII and XIX shown in Table 3-1. The relationbetween the rate of asphaltene decomposition and the amount of MoO₃ wasexamined after about 50 hours of operation. The results are shown inFIG. 10. These results indicate that such catalysts carrying onlymolybdenum as the catalytic metal component have a sufficiently highactivity for asphaltene decomposition, and that their activity increaseswith a decrease in the amount of molybdenum.

Example 2-7

The feedstock oils shown in Table 1 were hydrogen treated at atemperature of 405° C., a hydrogen pressure of 140 atm., a LHSV of 0.67hour⁻¹ and a hydrogen to oil ratio (N liter/liter) of 1,000 by usingCatalyst VII. Table 8 shows the properties of the oils produced afterabout 1,000 hours of operation. As is obvious from the results showntherein, the catalysts of this invention show a high rate of asphaltenedecomposition irrespective of the feedstock oil involved, and produceoil containing extremely little vanadium and nickel, and reducedquantities of sulfur, nitrogen and Conradson carbon residue, and havinga lower molecular weight. Thus, it will be understood that the catalystsof this invention are suitable for hydrotreating heavy hydrocarbon oilsas a means for their pretreatment. The oils produced were found to havemostly a molecular weight of about 200 to 2,000 and an average molecularweight not greater than 1,000. As is apparent from their chemicalanalysis, these oils can be easily formed into a high grade lighthydrocarbon oil if hydrotreated with a catalyst having a high activityfor reactions, such as hydrodesulfurization and hydrodenitrification.FIG. 11 compares the molecular weight distributions of the feedstock oiland the product obtained by hydrotreatment.

The oils obtained as described above were hydrotreated at a temperatureof 390° C., a hydrogen pressure of 140 atm., a LHSV of 0.5 hour⁻¹ and ahydrogen to oil ratio (N liter/liter) of 1,000 by using Catalyst XXwhich was suitable for hydrodesulfurization and hydrodenitrification ofoil fractions. Table 9 shows the properties of the oils thereby producedafter about 500 hours of operation. The results shown in Table 9 teachthat the two-stage hydrotreatment according to this invention iseffective for forming low sulfur fuel oil containing only 0.5% by weightof sulfur from a heavy oil containing asphaltenes.

                  TABLE 8                                                         ______________________________________                                        Properties of Hydrotreated oils                                                                              Gach                                                  Boscan                                                                              Atha-    Khafji   Saran  Kuwait                                         crude basca    vacuum   vacuum vacuum                                         oil   bitumen  residue  residue                                                                              residue                                        (II)  (I)      (J)      (K)    (L)                                     ______________________________________                                        Specific 20.5    17.5     14.2   14.8   13.2                                  gravity                                                                       API                                                                           Sulfur   1.74    2.01     2.43   1.63   2.78                                  wt %                                                                          Nitrogen 0.44    0.37     0.32   0.49   0.37                                  wt %                                                                          Conradson                                                                              7.4     6.8      13.8   11.1   14.4                                  carbon                                                                        residue                                                                       wt %                                                                          Asphaltenes                                                                            1.4     2.2      4.0    1.65   1.91                                  wt %                                                                          Metal                                                                         wt ppm                                                                        Ni       6       18       12     15     10                                    V        21      34       16     15     7                                     Average  850     720      540    555    580                                   mol wt                                                                        ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Properties of oils treated with two-stage hydrotreating process                                              Gach                                                  Boscan                                                                              Atha-    Khafji   Saran  Kuwait                                         crude basca    vacuum   vacuum vacuum                                         oil   bitumen  residue  residue                                                                              residue                                        (II)  (I)      (J)      (K)    (L)                                     ______________________________________                                        Specific 22.6    22.5     19.9   21.1   19.2                                  gravity                                                                       API                                                                           Sulfur   0.23    0.31     0.39   0.25   0.49                                  wt %                                                                          Nitrogen 0.26    0.29     0.21   0.29   0.29                                  wt %                                                                          Conradson                                                                              2.30    2.24     5.09   3.73   5.70                                  carbon                                                                        residue                                                                       wt %                                                                          Asphaltenes                                                                            0.67    1.16     2.11   0.84   1.09                                  wt %                                                                          Metal                                                                         wt ppm                                                                        Ni       1.3     8.3      5.5    5.8    5.2                                   V        2.9     14.9     5.1    3.5    1.8                                   ______________________________________                                    

Example 2-8

This example was intended for showing that the two-stage hydrotreatmentaccording to this invention is highly advantageous for the treatment ofheavy oil containing a large quantity of asphaltenes. For this purpose,Khafji vacuum residue was subjected to prolonged two-stagehydrotreatment under the conditions set forth in Table 10 by usingCatalyst VII of this invention for the first step of the process, andknown desulfurization catalyst XX for the second step. For the sake ofcomparison, one-stage hydrodesulfurization was carried out under theconditions set forth in Table 10 by using typically knowndesulfurization catalyst XXI. During these treatments, the reactiontemperature was raised with a reduction in the catalyst activity tomaintain a sulfur content of about 0.5% in the product. FIG. 12 showsthe reaction temperature varying with the lapse of time.

                  TABLE 10                                                        ______________________________________                                        Conditions for hydrotreatment                                                                      Two-stage                                                         One-stage   hydrodesulfurization                                              hydrodesulfurization                                                                      First step                                                                              Second step                                    ______________________________________                                        Hydrogen   140           140       140                                        pressure                                                                      (atm.)                                                                        LHSV (hour.sup.-1)                                                                       0.2           0.6       0.3                                        Hydrogen to oil                                                                          1,000         1,000     1,000                                      ratio (N lit./lit.)                                                           ______________________________________                                    

As is apparent from FIG. 12, the reaction temperature reached 425° C.after only about 3,500 hours of operation for one-stagehydrodesulfurization in a conventional manner. The temperature of 425°C. is the level at which an ordinary industrially operating desulfurizerends its operation. On the other hand, the two-stagehydrodesulfurization according to this invention did not have itsreaction temperature reach 420° C. even after about 8,000 hours ofoperation, and proved itself to be fully capable of operation for aslong a time as one year continuously.

Example 2-9

This example is intended for showing that the two-stage hydrotreatmentaccording to this invention makes it possible to produce oil capable ofbeing treated in an ordinary catalytic cracking apparatus, directly fromheavy oil containing a large quantity of heavy metals.

Gach Saran atmospheric residue was subjected to two-stage hydrotreatmentunder the conditions set forth in Table 11 by using the Catalyst VII ofthis invention for the first step of the process, and Catalyst XXIVobtained by adding boria to desulfurization catalyst XX, and thus havingan increased activity for denitrification and reduction of Conradsoncarbon residue, for the second step.

                  TABLE 11                                                        ______________________________________                                        Conditions for two-stage hydrotreatment                                                       First step                                                                            Second step                                           ______________________________________                                        Reaction temp. (°C.)                                                                     405       405                                               Hydrogen pressure (atm.)                                                                        140       140                                               LHSV (hr.sup.-1)  0.6       1.2                                               Hydrogen to oil ratio                                                                           1,000     1,000                                             (N liter/liter)                                                               ______________________________________                                    

Table 12 shows the properties of the oil produced after about 500 hoursof operation for the two-stage treatment. The oil thus produced had atotal vanadium and nickel content not greater than 10 ppm, and aConradson carbon residue content not greater than 4% by weight. This oilis, thus, suitable for catalytic cracking.

                  TABLE 12                                                        ______________________________________                                        Properties of oil produced                                                    Properties           Feedstock oil F                                          ______________________________________                                        Specific gravity (°API)                                                                     21.1                                                     Sulfur (wt %)        0.39                                                     Nitrogen (wt %)      0.21                                                     Conradson carbon residue (wt %)                                                                    3.7                                                      Asphaltenes (wt %)   0.3                                                      Metals (wt ppm): Nickel                                                                            1.4                                                      Vanadium             0.3                                                      ______________________________________                                    

Example 2-10

This example shows a combination of the two-stage process with otherprocesses, which is intended for obtaining light oil containingsubstantially no asphaltene or heavy metal, from heavy oil containing alarge quantity of asphaltenes. Tests were conducted by using a pilotplant constructed by connecting a solvent deasphalting process directlywith the first step of the two-stage process, so that the heavy fractionleaving the deasphalting process could be recycled into the first step,and the light oil leaving the deasphalting process could be subjected tothe second step of treatment.

Khafji vacuum residue C was supplied at a flow rate of 170 cc per hour,and mixed with a gas rich in hydrogen, so that a hydrogen to oil ratio(N liter/liter) of 1,000 could be obtained. This mixture was pre-heated,and supplied for the first step treatment. The first step treatment wascarried out by using a co-current downward flow type reactor providedwith a reaction vessel having an inside diameter of 50 mm, a length of3,000 mm and a relatively thick stainless steel wall, and filled with660 cc of Catalyst VII of this invention. The conditions for the firststep hydrotreatment were as shown in Table 13.

The product of the first step treatment was separated into a gas whichwas rich in hydrogen, and a substantially liquid reaction product. Thegas-liquid separation was carried out at 150° C. and a pressure whichwas substantially equal to that which had prevailed in the reactionvessel. The gas rich in hydrogen was cleaned of its impurities, such ashydrogen sulfide and ammonia, in an amine washing apparatus, and reusedafter it was mixed with the makeup hydrogen gas to be fed into thereaction process. About 10% of gas was removed from the system in wichthe gas containing light hydrocarbon gas was being circulated, so thatno undue elevation in the concentration of such light hydrocarbon gasmight occur. The liquid reaction product was delivered into thedeasphalting process.

                  TABLE 13                                                        ______________________________________                                        Conditions for hydrotreatment                                                                 First step                                                                            Second step                                           ______________________________________                                        Reaction temp. (°C.)                                                                     405       380                                               Hydrogen pressure (atm.)                                                                        140       90                                                LHSV (hr.sup.-1)  0.25*     1.0                                               Hydrogen to oil ratio                                                                           1,000     1,000                                             (N liter/liter)                                                               ______________________________________                                         *LHSV for new material                                                   

Deasphalting was carried out by using n-butane as a solvent, and at asolvent ratio of 7, an overhead extraction temperature of 135° C., abottom extraction temperature of 125° C. and a pressure of 40 atm. Thegreater part of the liquid reaction product obtained above was separatedinto the solvent phase. The solvent phase was introduced into a solventrecovery apparatus, and the solvent was separated by evaporation,whereby light oil containing substantially no asphaltene or heavy metalwas obtained. The heavy fraction remaining undissolved in the solventwas raised in pressure by heating at about 250° C., and recycled intothe first step of the hydrotreating process.

Deasphalting was carried out by a rotary disc extraction columncomprising a column having an inside diameter of 28 mm and a height of690 mm, and provided internally with 102 discs each having a diameter of18 mm, and a stationary zone attached to the bottom of the column, andhaving an inside diameter of 53.5 mm and a height of 515 mm. The heavyfraction from the deasphalting step was recycled into upstream of thezone where the oil was mixed with the gas rich in hydrogen.

The operation could be continued for about 600 hours. There was obtainedhigh grade light oil containing extremely little asphaltene and heavymetal. Its properties are shown in Table 14. The light oil could beproduced with a yield of at least 94.5% by weight, and the hydrogenconsumption was 820 SCF/BBL. A considerable degree of desulfurizationtook place in addition to the decomposition of asphaltene and removal ofmetal during the first step of treatment. In this example, adesulfurization rate of about 58% was observed.

The light oil thus obtained was, then, subjected to the second stephydrotreatment under the conditions set forth in Table 13 in thepresence of Catalyst XXIV, using an apparatus similar to that which hadbeen used for the first step. Table 14 shows the properties of the oilobtained after about 300 hours of operation. The oil showed a yield of92.6% by weight of the feedstock oil, with a hydrogen consumption of 455SCF/BBL.

                  TABLE 14                                                        ______________________________________                                        Properties of hydrotreated oil                                                                 Product from                                                                           Product from                                                         first step                                                                             second step                                         ______________________________________                                        Specific gravity (°API)                                                                   17.8       23.7                                            Sulfur (wt %)      2.11       0.21                                            Nitrogen (wt %)    0.31       0.10                                            Conradson carbon residue (wt %)                                                                  5.72       2.03                                            Asphaltenes (wt %) trace      trace                                           Metal (ppm): Nickel                                                                              0.4        0.03                                            Vanadium           0.1        0.01                                            ______________________________________                                    

The light oil ultimately obtained by the foregoing treatment containedsubstantially no asphaltenes, and had a very low metal content. Thus, itprovides an ideal starting material for ordinary hydrocracking,fluidized catalytic cracking, and the like.

Example 3-1 (Cracking of hydrotreated oil)

The oil obtained by treatment with hydrogen as set forth in Example 2-9was tested for catalytic cracking by using a riser type pilot plant. Thepilot plant consisted mainly of a catalyst feeding tank, a riserreactor, a stripper and a product recovery system. The catalyst was acommercially available equilibrium catalyst composed of zeolitedispersed in amorphous silica-alumina, and containing 60.4% by weight ofSiO₂, 36% by weight of Al₂ O₃, 2.8% by weight of Re₂ O₅, 0.5% by weightof Na, 20 ppm of Ni, 40 ppm of V and 2,700 ppm of Fe. The catalyst inthe feeding tank was maintained in fluidized form on a nitrogen stream,discharged through an orifice at the bottom of the tank, and introducedinto the feedstock oil feeding zone. The catalyst was mixed with the oilsupplied in atomized form through a spray nozzle, and the mixture wasdelivered into the riser reactor, in which the catalyst caused crackingof the oil. The riser reactor comprised a stainless pipe having aninside diameter of 3.2 mm and a length of 35 m, and which was, as awhole, held at a constant temperature by a salt bath containing bariumchloride. The operating conditions were controlled as shown in Table 15.

Table 16 shows a typical yield of the product obtained after above fivehours of normal operation under the conditions set forth in Table 15.The gasoline thus obtained had a research octane number of 91.0.

                  TABLE 15                                                        ______________________________________                                        Conditions for reaction                                                       ______________________________________                                        Reaction zone temp.   About 530° C.                                    Stripper temp.        About 530° C.                                    Catalyst feeding tank temp.                                                                         About 650° C.                                    Oil retention time in riser pipe                                                                    4.5 sec.                                                Catalyst/oil weight ratio                                                                           9.5                                                     Oil flow rate         540 g/h                                                 ______________________________________                                    

                  TABLE 16                                                        ______________________________________                                        Yield of product and conversion ratio                                         ______________________________________                                        Debutanized gasoline   55.0 vol. %                                            Total C.sub.4          14.3 vol. %                                            Total C.sub.3          13.0 vol. %                                            C.sub.2.sup.- -         5.2 wt %                                              Conversion rate (430° F.)                                                                     78.4 wt %                                              ______________________________________                                    

Example 3-2 (Cracking of hydrotreated oil)

The oil produced as set forth in Example 2-10 (of which the propertiesare shown in Table 14) was subjected to hydrocracking by using CatalystXX and the apparatus which had been used for the second step ofhydrotreatment in Example 2-10. The reaction was caused to take place ata temperature of 420° C., a hydrogen pressure of 180 atm., a LHSV of 0.3hour⁻¹ and a hydrogen to oil ratio (N liter/liter) of 1,000. The yieldsof the products obtained by hydrocracking and their properties are shownin Tables 17 and 18, respectively. Naphtha, kerosene and light oilshowed a total yield of 69.8 vol. %, with a hydrogen consumption of1,740 SCF/BBL.

                  TABLE 17                                                        ______________________________________                                        Yields of products obtained by hydrocracking                                  ______________________________________                                        H.sub.2 wt %     -2.7                                                         (SCF/BBL)        1,740                                                        H.sub.2 S + NH.sub.3 wt %                                                                      0.3                                                          C.sub.1 -C.sub.4 wt %                                                                          2.0                                                          Naphtha vol %    21.6                                                         (C.sub.5 - 350° F.)                                                    Kerosene vol %   15.7                                                         (350-450° F.)                                                          Light oil vol %  32.5                                                         (450-650° F.)                                                          Atmospheric residue                                                                            46.9                                                         (650° F..sup.+) vol %                                                  ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                        Properties of oils obtained by hydrocracking                                             Specific                 Aniline                                              gravity                                                                              Sulfur   Nitrogen point                                                °API                                                                          ppm      ppm      ° C.                               ______________________________________                                        Naphtha      56.7     trace     3     50                                      (C.sub.5 - 350° F.)                                                    Kerosene     40.0      4        5     48                                      (350-450° F.)                                                          Light oil    34.8     15       24     54                                      (450-650° F.)                                                          Atmospheric  26.6     110      290    84                                      residue (650° F.+)                                                     ______________________________________                                    

Example 2-11 (Hydrotreatment)

This example is directed to the preparation of the catalyst of thisinvention in the reaction system.

Boscan crude oil A was hydrotreated at a temperature of 405° C., ahydrogen pressure of 140 atm., a LHSV of 1.0 hour⁻¹ and a hydrogen tooil ratio (N liter/liter) of 1,000 in the presence of the aluminacarrier XV of this invention on which no catalytic metal component wassupported. The results shown in FIG. 13 were obtained. It will be notedfrom FIG. 13 that the alumina carrier showed an increasing activity forasphaltene decomposition with an increase in the deposition of vanadium(vanadyl sulfide), and this activity remained substantially constantafter the amount of vanadium deposited on the carrier exceeded about 10%by weight. Thus, the catalytic metal component for the catalyst of thisinvention does not always need to be attached to the carrier outside thereaction system, but may be appropriately formed within the reactionsystem, if vanadium and other metals contained in the feedstock oil areutilized. More specifically, a carrier which satisfies the requirementsspecified by this invention is brought into contact with a heavyhydrocarbon oil containing at least 200 ppm by weight of vanadium in ahydrogen atmosphere at a temperature of 350° C. to 450° C. and ahydrogen pressure of 50 to 250 atm., so that at least about 10% byweight of vanadium may be deposited on the carrier, and activated,whereby a catalyst having a desired activity can be formed in situ.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

We claim:
 1. A catalyst for hydrotreating a heavy hydrocarbon oilcontaining asphaltenes, comprising:a porous carrier composed of one ormore inorganic oxides of at least one member selected from the groupconsisting of the elements belonging to Groups II, III and IV of thePeriodic Table; and one or more catalytic metal components compositedwith said carrier, the metal of said catalytic metal components beingselected from the group consisting of the metals belonging to Groups VB,VIB, VIII and IB of the Periodic Table, said catalytic metal componentsbeing present in an amount of between about 0.1% and about 30% in termsof metal oxide based on the total weight of said catalyst, said catalysthaving the following pore characteristics (a)-(c) with regard to itspores having a diameter of 75 Å or more:(a) an average pore diameter APDbeing between about 180 and about 500 Å, (b) a total pore volume PV interms of cc/g being at least a value X calculated according to thefollowing equation: ##EQU10## the volume of pores with a diameter ofbetween about 180 and about 500 Å being at least about 0.35 cc/g, thevolume of pores with a diameter of at least 1500 Å being not greaterthan about 0.03 cc/g, and (c) a total surface area SA being at leastabout 104 m² /g, said catalyst having an average catalyst diameter ACDof at least about 0.6 mm.
 2. A catalyst as set forth in claim 1, whereinsaid total volume PV is not greater than a value X' calculated accordingto the following equation: ##EQU11## where ln is a symbol representing anatural logarithm.
 3. A catalyst as set forth in claim 1, wherein saidaverage pore diameter APD is between 180 Å and 400 Å, said total porevolume PV being between 0.5 cc/g and 1.5 cc/g, said total surface areaSA being at least 70 m² /g, the volume of pores with a diameter of notgreater than 100 Å being not greater than 0.1 cc/g, said averagecatalyst diameter ACD being between about 0.6 mm and about 1.5 mm.
 4. Acatalyst as set forth in claim 1, wherein the volume of pores having adiameter of between 180 Å and 400 Å is at least a half of the volume ofpores having a diameter of between 180 Å and 500 Å.
 5. A catalyst as setforth in claim 1, wherein said inorganic oxide is at least one memberselected from the group consisting of alumina, silica, titania, boria,zirconia, silica-alumina, silica-magnesia, alumina-magnesia,alumina-titania, silica-titania, alumina-boria, alumina-zirconia andsilica-zirconia.
 6. A catalyst as set forth in claim 1, wherein themetal of said one or more catalytic metal components is at least onemember selected from the group consisting of vanadium, chromium,molybdenum, tungsten, cobalt, nickel and copper, said catalytic metalcomponents being in the form of an elemental metal, an oxide, a sulfideor a mixture thereof.
 7. A catalyst as set forth in claim 1 or 6,wherein the metal of said one or more catalytic metal components is atleast one member selected from the group consisting of vanadium andmolybdenum, said catalytic metal components being present in an amountof between about 0.1% and about 10% in terms of metal oxide based on thetotal weight of said catalyst.
 8. A catalyst as set forth in claim 1,wherein said carrier is prepared from a hydrogel prepared by adding to aseed hydrosol of at least one member selected from the group consistingof hydroxides of the elements belonging to Groups II, III and IV of thePeriodic Table, while changing the pH value of the hydrosol to ahydrosol-dissolution region and to a hydrosol-precipitation regionalternately at least one time, at least one hydrosol forming substancecontaining an element selected from the group consisting of the elementsbelonging to Groups II, III and IV of the Periodic Table during thechange in the pH value to at least one side of the regions to effectgrowth of crystallites of the seed hydrosol to finally an aggregatehydrogel.
 9. A catalyst as set forth in claim 8, wherein the change ofthe pH value to at least one side of said regions is effected by addingthe hydrosol forming substance.
 10. A catalyst as set forth in claim 8,wherein the amount of the hydrosol forming substance added every time is2-200 mol % in terms of oxide based on the total amount of the hydrosolin terms of oxide.
 11. A catalyst as set forth in any one of claims 8through 10, wherein said seed hydrosol is selected from the groupconsisting of hydroxides of magnesium boron, aluminum, silicon,titanium, zirconium and mixtures thereof.
 12. A catalyst as set forth inclaim 11, wherein said hydrosol forming substance contains at least oneelement selected from the group consisting of magnesium, boron,aluminum, silicon, titanium and zirconium.
 13. A catalyst as set forthin claim 8, wherein said seed hydrosol is aluminum hydroxide and saidhydrosol forming substance contains aluminum, said hydrosol-dissolutionpH region being not greater than 5, said hydrosol-precipitation pHregion ranging from 9 to 11, and said hydrosol being maintained at atemperature of at least 50° C. for at least one minute in each of saidpH regions.
 14. A catalyst as set forth in claim 8, wherein the changein pH value is repeated 2-50 times.
 15. A catalyst as set forth in claim8, wherein a metal compound containing the metal of said catalytic metalcomponent is added to the hydrosol during the change in the pH value,whereby said catalytic metal component is composited with said carrier.16. A catalyst according to claim 14, wherein the metal compoundcontaining the metal of said catalytic metal component is added to thehydrosol so as to effect the pH change.
 17. A catalyst as set forth inclaim 8, and prepared by a method comprising the steps of:(a) providinga seed hydrosol of at least one member selected from the groupconsisting of hydroxides of the elements belonging to Groups II, III andIV of the Periodic Table; (b) mixing a first pH controlling agent withsaid hydrosol to adjust the pH of said hydrosol to a first region andmaintaining said hydrosol at said first pH region, while agitating it,at a temperature and for a period of time sufficient to dissolve finehydrosol particles; (c) then mixing a second pH controlling agent withsaid hydrosol to adjust the pH of said hydrosol to a second region, atleast one of said first and second pH controlling agents including atleast one hydrosol forming substance containing an element selected fromthe group consisting of the elements belonging to Groups II, III and IVof the Periodic Table, and maintaining said hydrosol at said second pHregion, while agitating it, at a temperature and for a period of timesufficient to cause deposition of the dissolved hydrosol and thehydrosol from said hydrosol forming substance on the undissolved seedhydrosol, steps (b) and (c) being conducted once or repeated in sequencemore than once so that said seed hydrosol is caused to grow to anaggregate hydrogel; (d) molding and drying said hydrogel; and (e)supporting said one or more catalyst metal components on said hydrogel.18. A catalyst as set forth in claim 17, wherein said method furthercomprises controlling the solid content of said hydrogel to 10 to 80% byweight before step (d).
 19. A catalyst as set forth in claim 18, whereinstep (e) is conducted after step (d) and wherein step (e) comprisesimpregnating said dried hydrogel with a solution containing at least onecompound containing the metal of said catalytic metal components,followed by drying and calcining.
 20. A catalyst as set forth in claim18, wherein said method further comprises calcining the dried hydrogelfrom step (d), step (e) being conducted after said calcination.
 21. Acatalyst as set forth in claim 20, wherein step (e) comprisesimpregnating said calcined hydrogel with a solution containing at leastone compound containing the metal of said catalytic metal components,followed by drying and calcining.
 22. A catalyst as set forth in claim20, wherein the metal of said catalytic metal components includesvanadium and wherein step (e) comprises bringing said calcined hydrogelinto direct contact with a heavy hydrocarbon oil containing at least 200ppm by weight of vanadium at a temperature of between 300° and 500° C.and a hydrogen pressure of between 30 and 250 atm.
 23. A catalyst as setforth in claim 17, wherein said seed hydrosol is selected from the groupconsisting of hydroxides of magnesium, boron, aluminum, silicon,titanium and zirconium and mixtures thereof.
 24. A catalyst as set forthin claim 17, wherein said seed hydrosol is aluminum hydroxide hydrosoland said hydrosol forming substance contains aluminum, said first pHregion being not greater than 5, said second pH region ranging from 6 to11, said hydrosol being maintained at a temperature of at least 50° C.for at least one minute in each of said first and second pH regions. 25.A catalyst as set forth in claim 24, wherein said seed aluminumhydroxide hydrosol is formed from a member selected from the groupconsisting of aluminum salts, aluminates and aluminum hydroxide.
 26. Acatalyst as set forth in claim 24, wherein step (a) includes mixing anacidic or alkaline material with an alkaline or acidic aqueous solutioncontaining aluminum at a temperature of at least 70° C. to obtain amixture having a pH value of between 6 and 11, and aging said mixture ata temperature of at least 70° C., whereby the seed aluminum hydroxidehydrosol is established.
 27. A catalyst as set forth in claim 24,wherein step (a) includes forming a slurry containing aluminumhydroxide, and subjecting the slurry to a hydrothermal treatmentconducted at a temperature of between about 100° and about 300° C.
 28. Acatalyst as set forth in claim 27, wherein said hydrothermal treatmentis carried out in the presence of at least one ion selected from thegroup consisting of chromate ion, molybdate ion and tungstate ion.
 29. Acatalyst as set forth in claim 24, wherein said first pH controllingagent includes an aluminum salt which turns acidic when hydrolized. 30.A catalyst as set forth in claim 24 or 29, wherein said second pHcontrolling agent includes an aluminate which turns alkaline whenhydrolized.